Baclofen: A GAMMA-AMINOBUTYRIC ACID derivative that is a specific agonist of GABA-B RECEPTORS. It is used in the treatment of MUSCLE SPASTICITY, especially that due to SPINAL CORD INJURIES. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.Receptors, GABA-B: A subset of GABA RECEPTORS that signal through their interaction with HETEROTRIMERIC G-PROTEINS.GABA Agonists: Endogenous compounds and drugs that bind to and activate GAMMA-AMINOBUTYRIC ACID receptors (RECEPTORS, GABA).Receptor, Serotonin, 5-HT1B: A serotonin receptor subtype found at high levels in the BASAL GANGLIA and the frontal cortex. It plays a role as a terminal autoreceptor that regulates the rate of SEROTONIN release from nerve endings. This serotonin receptor subtype is closely related to and has similar drug binding properties as the 5-HT1D RECEPTOR. It is particularly sensitive to the agonist SUMATRIPTAN and may be involved in mediating the drug's antimigraine effect.Receptor, Serotonin, 5-HT2B: A serotonin receptor subtype found in the BRAIN; HEART; LUNGS; PLACENTA and DIGESTIVE SYSTEM organs. A number of functions have been attributed to the action of the 5-HT2B receptor including the development of cardiac myocytes (MYOCYTES, CARDIAC) and the contraction of SMOOTH MUSCLE.Receptor, Endothelin B: A subtype of endothelin receptor found predominantly in the KIDNEY. It may play a role in reducing systemic ENDOTHELIN levels.Serotonin Antagonists: Drugs that bind to but do not activate serotonin receptors, thereby blocking the actions of serotonin or SEROTONIN RECEPTOR AGONISTS.Receptors, Endothelin: Cell surface proteins that bind ENDOTHELINS with high affinity and trigger intracellular changes which influence the behavior of cells.Receptors, Serotonin: Cell-surface proteins that bind SEROTONIN and trigger intracellular changes which influence the behavior of cells. Several types of serotonin receptors have been recognized which differ in their pharmacology, molecular biology, and mode of action.Serotonin Receptor Agonists: Endogenous compounds and drugs that bind to and activate SEROTONIN RECEPTORS. Many serotonin receptor agonists are used as ANTIDEPRESSANTS; ANXIOLYTICS; and in the treatment of MIGRAINE DISORDERS.Receptors, Vasopressin: Specific molecular sites or proteins on or in cells to which VASOPRESSINS bind or interact in order to modify the function of the cells. Two types of vasopressin receptor exist, the V1 receptor in the vascular smooth muscle and the V2 receptor in the kidneys. The V1 receptor can be subdivided into V1a and V1b (formerly V3) receptors.GABA Agents: Substances used for their pharmacological actions on GABAergic systems. GABAergic agents include agonists, antagonists, degradation or uptake inhibitors, depleters, precursors, and modulators of receptor function.Adenosine A2 Receptor Antagonists: Compounds that selectively bind to and block the activation of ADENOSINE A2 RECEPTORS.Anti-Anxiety Agents: Agents that alleviate ANXIETY, tension, and ANXIETY DISORDERS, promote sedation, and have a calming effect without affecting clarity of consciousness or neurologic conditions. ADRENERGIC BETA-ANTAGONISTS are commonly used in the symptomatic treatment of anxiety but are not included here.Indoles: Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.PyrrolidinesPiperidines: A family of hexahydropyridines.GABA Antagonists: Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.GABA-B Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-B RECEPTORS.Receptor, Endothelin A: A subtype of endothelin receptor found predominantly in the VASCULAR SMOOTH MUSCLE. It has a high affinity for ENDOTHELIN-1 and ENDOTHELIN-2.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Receptor, Adenosine A2B: A subclass of adenosine A2 receptors found in the CECUM, the COLON, the BLADDER, and a variety of other tissues. It is generally considered to be a low affinity receptor for ADENOSINE that couples to the GS, STIMULATORY G-PROTEIN.Peptides, Cyclic: Peptides whose amino and carboxy ends are linked together with a peptide bond forming a circular chain. Some of them are ANTI-INFECTIVE AGENTS. Some of them are biosynthesized non-ribosomally (PEPTIDE BIOSYNTHESIS, NON-RIBOSOMAL).Endothelins: 21-Amino-acid peptides produced by vascular endothelial cells and functioning as potent vasoconstrictors. The endothelin family consists of three members, ENDOTHELIN-1; ENDOTHELIN-2; and ENDOTHELIN-3. All three peptides contain 21 amino acids, but vary in amino acid composition. The three peptides produce vasoconstrictor and pressor responses in various parts of the body. However, the quantitative profiles of the pharmacological activities are considerably different among the three isopeptides.Serotonin: A biochemical messenger and regulator, synthesized from the essential amino acid L-TRYPTOPHAN. In humans it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets. Serotonin mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity. Multiple receptor families (RECEPTORS, SEROTONIN) explain the broad physiological actions and distribution of this biochemical mediator.Interleukin 1 Receptor Antagonist Protein: A ligand that binds to but fails to activate the INTERLEUKIN 1 RECEPTOR. It plays an inhibitory role in the regulation of INFLAMMATION and FEVER. Several isoforms of the protein exist due to multiple ALTERNATIVE SPLICING of its mRNA.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Endothelin-1: A 21-amino acid peptide produced in a variety of tissues including endothelial and vascular smooth-muscle cells, neurons and astrocytes in the central nervous system, and endometrial cells. It acts as a modulator of vasomotor tone, cell proliferation, and hormone production. (N Eng J Med 1995;333(6):356-63)Receptors, GABA: Cell-surface proteins that bind GAMMA-AMINOBUTYRIC ACID with high affinity and trigger changes that influence the behavior of cells. GABA-A receptors control chloride channels formed by the receptor complex itself. They are blocked by bicuculline and usually have modulatory sites sensitive to benzodiazepines and barbiturates. GABA-B receptors act through G-proteins on several effector systems, are insensitive to bicuculline, and have a high affinity for L-baclofen.Receptors, Complement 3b: Molecular sites on or in some B-lymphocytes and macrophages that recognize and combine with COMPLEMENT C3B. The primary structure of these receptors reveal that they contain transmembrane and cytoplasmic domains, with their extracellular portion composed entirely of thirty short consensus repeats each having 60 to 70 amino acids.Sulfonamides: A group of compounds that contain the structure SO2NH2.Pyridines: Compounds with a six membered aromatic ring containing NITROGEN. The saturated version is PIPERIDINES.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Neurokinin-1 Receptor Antagonists: Compounds that inhibit or block the activity of NEUROKININ-1 RECEPTORS.Purinergic P1 Receptor Antagonists: Compounds that bind to and block the stimulation of PURINERGIC P1 RECEPTORS.Serotonin 5-HT2 Receptor Antagonists: Drugs that bind to but do not activate SEROTONIN 5-HT2 RECEPTORS, thereby blocking the actions of SEROTONIN or SEROTONIN 5-HT2 RECEPTOR AGONISTS. Included under this heading are antagonists for one or more specific 5-HT2 receptor subtypes.Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.Receptors, GABA-A: Cell surface proteins which bind GAMMA-AMINOBUTYRIC ACID and contain an integral membrane chloride channel. Each receptor is assembled as a pentamer from a pool of at least 19 different possible subunits. The receptors belong to a superfamily that share a common CYSTEINE loop.GABA Modulators: Substances that do not act as agonists or antagonists but do affect the GAMMA-AMINOBUTYRIC ACID receptor-ionophore complex. GABA-A receptors (RECEPTORS, GABA-A) appear to have at least three allosteric sites at which modulators act: a site at which BENZODIAZEPINES act by increasing the opening frequency of GAMMA-AMINOBUTYRIC ACID-activated chloride channels; a site at which BARBITURATES act to prolong the duration of channel opening; and a site at which some steroids may act. GENERAL ANESTHETICS probably act at least partly by potentiating GABAergic responses, but they are not included here.GABA-A Receptor Antagonists: Drugs that bind to but do not activate GABA-A RECEPTORS thereby blocking the actions of endogenous or exogenous GABA-A RECEPTOR AGONISTS.Histamine H2 Antagonists: Drugs that selectively bind to but do not activate histamine H2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood.Serotonin 5-HT3 Receptor Antagonists: Drugs that bind to but do not activate SEROTONIN 5-HT3 RECEPTORS, thereby blocking the actions of SEROTONIN or SEROTONIN 5-HT3 RECEPTOR AGONISTS.Dopamine Antagonists: Drugs that bind to but do not activate DOPAMINE RECEPTORS, thereby blocking the actions of dopamine or exogenous agonists. Many drugs used in the treatment of psychotic disorders (ANTIPSYCHOTIC AGENTS) are dopamine antagonists, although their therapeutic effects may be due to long-term adjustments of the brain rather than to the acute effects of blocking dopamine receptors. Dopamine antagonists have been used for several other clinical purposes including as ANTIEMETICS, in the treatment of Tourette syndrome, and for hiccup. Dopamine receptor blockade is associated with NEUROLEPTIC MALIGNANT SYNDROME.Angiotensin Receptor Antagonists: Agents that antagonize ANGIOTENSIN RECEPTORS. Many drugs in this class specifically target the ANGIOTENSIN TYPE 1 RECEPTOR.Serotonin 5-HT1 Receptor Antagonists: Drugs that bind to but do not activate SEROTONIN 5-HT1 RECEPTORS, thereby blocking the actions of SEROTONIN 5-HT1 RECEPTOR AGONISTS. Included under this heading are antagonists for one or more of the specific 5-HT1 receptor subtypes.Hormone Antagonists: Chemical substances which inhibit the function of the endocrine glands, the biosynthesis of their secreted hormones, or the action of hormones upon their specific sites.GABA Plasma Membrane Transport Proteins: A family of plasma membrane neurotransmitter transporter proteins that regulates extracellular levels of the inhibitory neurotransmitter GAMMA-AMINOBUTYRIC ACID. They differ from GABA RECEPTORS, which signal cellular responses to GAMMA-AMINOBUTYRIC ACID. They control GABA reuptake into PRESYNAPTIC TERMINALS in the CENTRAL NERVOUS SYSTEM through high-affinity sodium-dependent transport.Adenosine A1 Receptor Antagonists: Compounds that bind to and block the stimulation of ADENOSINE A1 RECEPTORS.Receptors, N-Methyl-D-Aspartate: A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.Purinergic P2 Receptor Antagonists: Compounds that bind to and block the stimulation of PURINERGIC P2 RECEPTORS.GABA-B Receptor Antagonists: Drugs that bind to but do not activate GABA-B RECEPTORS thereby blocking the actions of endogenous or exogenous GABA-B RECEPTOR AGONISTS.Bicuculline: An isoquinoline alkaloid obtained from Dicentra cucullaria and other plants. It is a competitive antagonist for GABA-A receptors.Narcotic Antagonists: Agents inhibiting the effect of narcotics on the central nervous system.Histamine H1 Antagonists: Drugs that selectively bind to but do not activate histamine H1 receptors, thereby blocking the actions of endogenous histamine. Included here are the classical antihistaminics that antagonize or prevent the action of histamine mainly in immediate hypersensitivity. They act in the bronchi, capillaries, and some other smooth muscles, and are used to prevent or allay motion sickness, seasonal rhinitis, and allergic dermatitis and to induce somnolence. The effects of blocking central nervous system H1 receptors are not as well understood.Muscarinic Antagonists: Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.Receptors, Complement: Molecules on the surface of some B-lymphocytes and macrophages, that recognize and combine with the C3b, C3d, C1q, and C4b components of complement.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Histamine Antagonists: Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonists. Classical antihistaminics block the histamine H1 receptors only.Xanthines: Purine bases found in body tissues and fluids and in some plants.Radioligand Assay: Quantitative determination of receptor (binding) proteins in body fluids or tissue using radioactively labeled binding reagents (e.g., antibodies, intracellular receptors, plasma binders).Sialoglycoproteins: Glycoproteins which contain sialic acid as one of their carbohydrates. They are often found on or in the cell or tissue membranes and participate in a variety of biological activities.Leukotriene Antagonists: A class of drugs designed to prevent leukotriene synthesis or activity by blocking binding at the receptor level.Dizocilpine Maleate: A potent noncompetitive antagonist of the NMDA receptor (RECEPTORS, N-METHYL-D-ASPARTATE) used mainly as a research tool. The drug has been considered for the wide variety of neurodegenerative conditions or disorders in which NMDA receptors may play an important role. Its use has been primarily limited to animal and tissue experiments because of its psychotropic effects.Receptors, Purinergic P1: A class of cell surface receptors that prefer ADENOSINE to other endogenous PURINES. Purinergic P1 receptors are widespread in the body including the cardiovascular, respiratory, immune, and nervous systems. There are at least two pharmacologically distinguishable types (A1 and A2, or Ri and Ra).Receptor, Cholecystokinin B: A subtype of cholecystokinin receptor found primarily in the CENTRAL NERVOUS SYSTEM and the GASTRIC MUCOSA. It may play a role as a neuromodulator of dopaminergic neurotransmission the regulation of GASTRIC ACID secretion from GASTRIC PARIETAL CELLS.Benzazepines: Compounds with BENZENE fused to AZEPINES.Biphenyl CompoundsGABA Uptake Inhibitors: Compounds that suppress or block the plasma membrane transport of GAMMA-AMINOBUTYRIC ACID by GABA PLASMA MEMBRANE TRANSPORT PROTEINS.Receptors, Cholecystokinin: Cell surface proteins that bind cholecystokinin (CCK) with high affinity and trigger intracellular changes influencing the behavior of cells. Cholecystokinin receptors are activated by GASTRIN as well as by CCK-4; CCK-8; and CCK-33. Activation of these receptors evokes secretion of AMYLASE by pancreatic acinar cells, acid and PEPSIN by stomach mucosal cells, and contraction of the PYLORUS and GALLBLADDER. The role of the widespread CCK receptors in the central nervous system is not well understood.GABA-A Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-A RECEPTORS.Drug Interactions: The action of a drug that may affect the activity, metabolism, or toxicity of another drug.Adenosine: A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.TetrazolesSynaptic Transmission: The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Muscimol: A neurotoxic isoxazole isolated from species of AMANITA. It is obtained by decarboxylation of IBOTENIC ACID. Muscimol is a potent agonist of GABA-A RECEPTORS and is used mainly as an experimental tool in animal and tissue studies.Receptors, Interleukin-1: Cell surface receptors that are specific for INTERLEUKIN-1. Included under this heading are signaling receptors, non-signaling receptors and accessory proteins required for receptor signaling. Signaling from interleukin-1 receptors occurs via interaction with SIGNAL TRANSDUCING ADAPTOR PROTEINS such as MYELOID DIFFERENTIATION FACTOR 88.Phosphinic Acids: Inorganic or organic derivatives of phosphinic acid, H2PO(OH). They include phosphinates and phosphinic acid esters.Behavior, Animal: The observable response an animal makes to any situation.Ketanserin: A selective serotonin receptor antagonist with weak adrenergic receptor blocking properties. The drug is effective in lowering blood pressure in essential hypertension. It also inhibits platelet aggregation. It is well tolerated and is particularly effective in older patients.Adrenergic alpha-1 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC ALPHA-1 RECEPTORS.Nicotinic Antagonists: Drugs that bind to nicotinic cholinergic receptors (RECEPTORS, NICOTINIC) and block the actions of acetylcholine or cholinergic agonists. Nicotinic antagonists block synaptic transmission at autonomic ganglia, the skeletal neuromuscular junction, and at central nervous system nicotinic synapses.Glutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Binding, Competitive: The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.PiperazinesNeural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.QuinoxalinesElectric Stimulation: Use of electric potential or currents to elicit biological responses.Pyrazoles: Azoles of two nitrogens at the 1,2 positions, next to each other, in contrast with IMIDAZOLES in which they are at the 1,3 positions.Patch-Clamp Techniques: An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.Devazepide: A derivative of benzodiazepine that acts on the cholecystokinin A (CCKA) receptor to antagonize CCK-8's (SINCALIDE) physiological and behavioral effects, such as pancreatic stimulation and inhibition of feeding.Purinergic P1 Receptor Agonists: Compounds that bind to and stimulate PURINERGIC P1 RECEPTORS.Picrotoxin: A noncompetitive antagonist at GABA-A receptors and thus a convulsant. Picrotoxin blocks the GAMMA-AMINOBUTYRIC ACID-activated chloride ionophore. Although it is most often used as a research tool, it has been used as a CNS stimulant and an antidote in poisoning by CNS depressants, especially the barbiturates.Adrenergic alpha-2 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC ALPHA-2 RECEPTORS.Histamine H3 Antagonists: Drugs that selectively bind to but do not activate HISTAMINE H3 RECEPTORS. They have been used to correct SLEEP WAKE DISORDERS and MEMORY DISORDERS.Losartan: An antagonist of ANGIOTENSIN TYPE 1 RECEPTOR with antihypertensive activity due to the reduced pressor effect of ANGIOTENSIN II.Hippocampus: A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.2-Amino-5-phosphonovalerate: The D-enantiomer is a potent and specific antagonist of NMDA glutamate receptors (RECEPTORS, N-METHYL-D-ASPARTATE). The L form is inactive at NMDA receptors but may affect the AP4 (2-amino-4-phosphonobutyrate; APB) excitatory amino acid receptors.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Receptor, Adenosine A2A: A subclass of adenosine A2 receptors found in LEUKOCYTES, the SPLEEN, the THYMUS and a variety of other tissues. It is generally considered to be a receptor for ADENOSINE that couples to the GS, STIMULATORY G-PROTEIN.Substance P: An eleven-amino acid neurotransmitter that appears in both the central and peripheral nervous systems. It is involved in transmission of PAIN, causes rapid contractions of the gastrointestinal smooth muscle, and modulates inflammatory and immune responses.Receptor, Serotonin, 5-HT2A: A serotonin receptor subtype found widely distributed in peripheral tissues where it mediates the contractile responses of variety of tissues that contain SMOOTH MUSCLE. Selective 5-HT2A receptor antagonists include KETANSERIN. The 5-HT2A subtype is also located in BASAL GANGLIA and CEREBRAL CORTEX of the BRAIN where it mediates the effects of HALLUCINOGENS such as LSD.Receptors, Neurokinin-1: A class of cell surface receptors for TACHYKININS with a preference for SUBSTANCE P. Neurokinin-1 (NK-1) receptors have been cloned and are members of the G protein coupled receptor superfamily. They are found on many cell types including central and peripheral neurons, smooth muscle cells, acinar cells, endothelial cells, fibroblasts, and immune cells.Serotonin 5-HT1 Receptor Agonists: Endogenous compounds and drugs that specifically stimulate SEROTONIN 5-HT1 RECEPTORS. Included under this heading are agonists for one or more of the specific 5-HT1 receptor subtypes.Adenosine A3 Receptor Antagonists: Compounds that selectively bind to and block the activation of ADENOSINE A3 RECEPTORS.Ritanserin: A selective and potent serotonin-2 antagonist that is effective in the treatment of a variety of syndromes related to anxiety and depression. The drug also improves the subjective quality of sleep and decreases portal pressure.Spiro Compounds: A group of compounds consisting in part of two rings sharing one atom (usually a carbon) in common.Azepines: Seven membered heterocyclic rings containing a NITROGEN atom.Receptors, Bradykinin: Cell surface receptors that bind BRADYKININ and related KININS with high affinity and trigger intracellular changes which influence the behavior of cells. The identified receptor types (B-1 and B-2, or BK-1 and BK-2) recognize endogenous KALLIDIN; t-kinins; and certain bradykinin fragments as well as bradykinin itself.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Cimetidine: A histamine congener, it competitively inhibits HISTAMINE binding to HISTAMINE H2 RECEPTORS. Cimetidine has a range of pharmacological actions. It inhibits GASTRIC ACID secretion, as well as PEPSIN and GASTRIN output.Receptor, Cannabinoid, CB1: A subclass of cannabinoid receptor found primarily on central and peripheral NEURONS where it may play a role modulating NEUROTRANSMITTER release.Pyridazines8-Hydroxy-2-(di-n-propylamino)tetralin: A serotonin 1A-receptor agonist that is used experimentally to test the effects of serotonin.Nipecotic AcidsReceptors, Serotonin, 5-HT1: A subclass of G-protein coupled SEROTONIN receptors that couple preferentially to GI-GO G-PROTEINS resulting in decreased intracellular CYCLIC AMP levels.Purinergic P2X Receptor Antagonists: Compounds that bind to and block the stimulation of PURINERGIC P2X RECEPTORS. Included under this heading are antagonists for specific P2X receptor subtypes.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.BenzodiazepinonesBenzimidazoles: Compounds with a BENZENE fused to IMIDAZOLES.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Receptor, Serotonin, 5-HT1D: A serotonin receptor subtype that is localized to the CAUDATE NUCLEUS; PUTAMEN; the NUCLEUS ACCUMBENS; the HIPPOCAMPUS, and the RAPHE NUCLEI. It plays a role as a terminal autoreceptor that regulates the rate of SEROTONIN release from nerve endings. This serotonin receptor subtype is closely related to and has similar drug binding properties as the 5-HT1B RECEPTOR, but is expressed at low levels. It is particularly sensitive to the agonist SUMATRIPTAN and may be involved in mediating the drug's antimigrane effect.Receptors, Dopamine D2: A subfamily of G-PROTEIN-COUPLED RECEPTORS that bind the neurotransmitter DOPAMINE and modulate its effects. D2-class receptor genes contain INTRONS, and the receptors inhibit ADENYLYL CYCLASES.N-Methylaspartate: An amino acid that, as the D-isomer, is the defining agonist for the NMDA receptor subtype of glutamate receptors (RECEPTORS, NMDA).Receptors, Dopamine D1: A subfamily of G-PROTEIN-COUPLED RECEPTORS that bind the neurotransmitter DOPAMINE and modulate its effects. D1-class receptor genes lack INTRONS, and the receptors stimulate ADENYLYL CYCLASES.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.Injections, Intraventricular: Injections into the cerebral ventricles.Serotonin 5-HT4 Receptor Antagonists: Drugs that bind to but do not activate SEROTONIN 5-HT4 RECEPTORS, thereby blocking the actions of SEROTONIN or SEROTONIN RECEPTOR AGONISTS.Naltrexone: Derivative of noroxymorphone that is the N-cyclopropylmethyl congener of NALOXONE. It is a narcotic antagonist that is effective orally, longer lasting and more potent than naloxone, and has been proposed for the treatment of heroin addiction. The FDA has approved naltrexone for the treatment of alcohol dependence.Oligopeptides: Peptides composed of between two and twelve amino acids.Dopamine: One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action.Adenosine-5'-(N-ethylcarboxamide): A stable adenosine A1 and A2 receptor agonist. Experimentally, it inhibits cAMP and cGMP phosphodiesterase activity.Angiotensin II: An octapeptide that is a potent but labile vasoconstrictor. It is produced from angiotensin I after the removal of two amino acids at the C-terminal by ANGIOTENSIN CONVERTING ENZYME. The amino acid in position 5 varies in different species. To block VASOCONSTRICTION and HYPERTENSION effect of angiotensin II, patients are often treated with ACE INHIBITORS or with ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKERS.Mice, Inbred C57BLNaloxone: A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.Adrenergic alpha-Antagonists: Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma.Receptors, Serotonin, 5-HT3: A subclass of serotonin receptors that form cation channels and mediate signal transduction by depolarizing the cell membrane. The cation channels are formed from 5 receptor subunits. When stimulated the receptors allow the selective passage of SODIUM; POTASSIUM; and CALCIUM.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Receptors, Thromboxane: Cell surface proteins that bind THROMBOXANES with high affinity and trigger intracellular changes influencing the behavior of cells. Some thromboxane receptors act via the inositol phosphate and diacylglycerol second messenger systems.Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Motor Activity: The physical activity of a human or an animal as a behavioral phenomenon.Famotidine: A competitive histamine H2-receptor antagonist. Its main pharmacodynamic effect is the inhibition of gastric secretion.Bradykinin: A nonapeptide messenger that is enzymatically produced from KALLIDIN in the blood where it is a potent but short-lived agent of arteriolar dilation and increased capillary permeability. Bradykinin is also released from MAST CELLS during asthma attacks, from gut walls as a gastrointestinal vasodilator, from damaged tissues as a pain signal, and may be a neurotransmitter.Excitatory Postsynaptic Potentials: Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.QuinolinesReceptors, Neurokinin-2: A class of cell surface receptors for tachykinins that prefers neurokinin A; (NKA, substance K, neurokinin alpha, neuromedin L), neuropeptide K; (NPK); or neuropeptide gamma over other tachykinins. Neurokinin-2 (NK-2) receptors have been cloned and are similar to other G-protein coupled receptors.Cannabinoid Receptor Antagonists: Compounds that inhibit or block the activity of CANNABINOID RECEPTORS.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Receptors, Angiotensin: Cell surface proteins that bind ANGIOTENSINS and trigger intracellular changes influencing the behavior of cells.Histamine: An amine derived by enzymatic decarboxylation of HISTIDINE. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter.Complement C3b: The larger fragment generated from the cleavage of COMPLEMENT C3 by C3 CONVERTASE. It is a constituent of the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb), and COMPLEMENT C5 CONVERTASES in both the classical (C4b2a3b) and the alternative (C3bBb3b) pathway. C3b participates in IMMUNE ADHERENCE REACTION and enhances PHAGOCYTOSIS. It can be inactivated (iC3b) or cleaved by various proteases to yield fragments such as COMPLEMENT C3C; COMPLEMENT C3D; C3e; C3f; and C3g.Vasoconstriction: The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.Receptor, Angiotensin, Type 1: An angiotensin receptor subtype that is expressed at high levels in a variety of adult tissues including the CARDIOVASCULAR SYSTEM, the KIDNEY, the ENDOCRINE SYSTEM and the NERVOUS SYSTEM. Activation of the type 1 angiotensin receptor causes VASOCONSTRICTION and sodium retention.QuinuclidinesAdrenergic Antagonists: Drugs that bind to but do not activate ADRENERGIC RECEPTORS. Adrenergic antagonists block the actions of the endogenous adrenergic transmitters EPINEPHRINE and NOREPINEPHRINE.Adrenergic beta-2 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC BETA-2 RECEPTORS.Receptors, Histamine H3: A class of histamine receptors discriminated by their pharmacology and mode of action. Histamine H3 receptors were first recognized as inhibitory autoreceptors on histamine-containing nerve terminals and have since been shown to regulate the release of several neurotransmitters in the central and peripheral nervous systems. (From Biochem Soc Trans 1992 Feb;20(1):122-5)Synapses: Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.Mineralocorticoid Receptor Antagonists: Drugs that bind to and block the activation of MINERALOCORTICOID RECEPTORS by MINERALOCORTICOIDS such as ALDOSTERONE.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Receptors, Opioid: Cell membrane proteins that bind opioids and trigger intracellular changes which influence the behavior of cells. The endogenous ligands for opioid receptors in mammals include three families of peptides, the enkephalins, endorphins, and dynorphins. The receptor classes include mu, delta, and kappa receptors. Sigma receptors bind several psychoactive substances, including certain opioids, but their endogenous ligands are not known.Imidazoles: Compounds containing 1,3-diazole, a five membered aromatic ring containing two nitrogen atoms separated by one of the carbons. Chemically reduced ones include IMIDAZOLINES and IMIDAZOLIDINES. Distinguish from 1,2-diazole (PYRAZOLES).Viper Venoms: Venoms from SNAKES of the viperid family. They tend to be less toxic than elapid or hydrophid venoms and act mainly on the vascular system, interfering with coagulation and capillary membrane integrity and are highly cytotoxic. They contain large amounts of several enzymes, other factors, and some toxins.6-Cyano-7-nitroquinoxaline-2,3-dione: A potent excitatory amino acid antagonist with a preference for non-NMDA iontropic receptors. It is used primarily as a research tool.Diazepam: A benzodiazepine with anticonvulsant, anxiolytic, sedative, muscle relaxant, and amnesic properties and a long duration of action. Its actions are mediated by enhancement of GAMMA-AMINOBUTYRIC ACID activity.CHO Cells: CELL LINE derived from the ovary of the Chinese hamster, Cricetulus griseus (CRICETULUS). The species is a favorite for cytogenetic studies because of its small chromosome number. The cell line has provided model systems for the study of genetic alterations in cultured mammalian cells.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Pyrilamine: A histamine H1 antagonist. It has mild hypnotic properties and some local anesthetic action and is used for allergies (including skin eruptions) both parenterally and locally. It is a common ingredient of cold remedies.Glycine: A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter.Receptors, Serotonin, 5-HT4: A subtype of G-protein-coupled SEROTONIN receptors that preferentially couple to GS STIMULATORY G-PROTEINS resulting in increased intracellular CYCLIC AMP. Several isoforms of the receptor exist due to ALTERNATIVE SPLICING of its mRNA.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.Membrane Potentials: The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).Antihypertensive Agents: Drugs used in the treatment of acute or chronic vascular HYPERTENSION regardless of pharmacological mechanism. Among the antihypertensive agents are DIURETICS; (especially DIURETICS, THIAZIDE); ADRENERGIC BETA-ANTAGONISTS; ADRENERGIC ALPHA-ANTAGONISTS; ANGIOTENSIN-CONVERTING ENZYME INHIBITORS; CALCIUM CHANNEL BLOCKERS; GANGLIONIC BLOCKERS; and VASODILATOR AGENTS.Receptor, Bradykinin B2: A constitutively expressed subtype of bradykinin receptor that may play a role in the acute phase of the inflammatory and pain response. It has high specificity for intact forms of BRADYKININ and KALLIDIN. The receptor is coupled to G-PROTEIN, GQ-G11 ALPHA FAMILY and G-PROTEIN, GI-GO ALPHA FAMILY signaling proteins.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Receptors, Bombesin: Cell surface proteins that bind bombesin or closely related peptides with high affinity and trigger intracellular changes influencing the behavior of cells. Gastrin- releasing peptide (GRP); GRP 18-27 (neuromedin C), and neuromedin B are endogenous ligands of bombesin receptors in mammals.PhenylpropionatesReceptors, Opioid, mu: A class of opioid receptors recognized by its pharmacological profile. Mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. They have also been shown to be molecular receptors for morphine.Capsaicin: An alkylamide found in CAPSICUM that acts at TRPV CATION CHANNELS.Excitatory Amino Acid Agonists: Drugs that bind to and activate excitatory amino acid receptors.Receptors, Neurotransmitter: Cell surface receptors that bind signalling molecules released by neurons and convert these signals into intracellular changes influencing the behavior of cells. Neurotransmitter is used here in its most general sense, including not only messengers that act to regulate ion channels, but also those which act on second messenger systems and those which may act at a distance from their release sites. Included are receptors for neuromodulators, neuroregulators, neuromediators, and neurohumors, whether or not located at synapses.Animals, Newborn: Refers to animals in the period of time just after birth.Cyclic AMP: An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.Cholecystokinin: A peptide, of about 33 amino acids, secreted by the upper INTESTINAL MUCOSA and also found in the central nervous system. It causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. Cholecystokinin may be the mediator of satiety.Receptors, Corticotropin-Releasing Hormone: Cell surface proteins that bind corticotropin-releasing hormone with high affinity and trigger intracellular changes which influence the behavior of cells. The corticotropin releasing-hormone receptors on anterior pituitary cells mediate the stimulation of corticotropin release by hypothalamic corticotropin releasing factor. The physiological consequence of activating corticotropin-releasing hormone receptors on central neurons is not well understood.Receptors, G-Protein-Coupled: The largest family of cell surface receptors involved in SIGNAL TRANSDUCTION. They share a common structure and signal through HETEROTRIMERIC G-PROTEINS.TriazolesReceptor, Serotonin, 5-HT2C: A serotonin receptor subtype found primarily in the CENTRAL NERVOUS SYSTEM and the CHOROID PLEXUS. This receptor subtype is believed to mediate the anorectic action of SEROTONIN, while selective antagonists of the 5-HT2C receptor appear to induce ANXIETY. Several isoforms of this receptor subtype exist, due to adenine deaminase editing of the receptor mRNA.Morphine: The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle.Arginine Vasopressin: The predominant form of mammalian antidiuretic hormone. It is a nonapeptide containing an ARGININE at residue 8 and two disulfide-linked cysteines at residues of 1 and 6. Arg-vasopressin is used to treat DIABETES INSIPIDUS or to improve vasomotor tone and BLOOD PRESSURE.OxadiazolesMorpholinesAnalysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Isoindoles: Benzopyrroles with the nitrogen at the number two carbon, in contrast to INDOLES which have the nitrogen adjacent to the six-membered ring.Receptors, Calcitonin Gene-Related Peptide: Cell surface proteins that bind CALCITONIN GENE-RELATED PEPTIDE with high affinity and trigger intracellular changes which influence the behavior of cells. CGRP receptors are present in both the CENTRAL NERVOUS SYSTEM and the periphery. They are formed via the heterodimerization of the CALCITONIN RECEPTOR-LIKE PROTEIN and RECEPTOR ACTIVITY-MODIFYING PROTEIN 1.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Adenosine A2 Receptor Agonists: Compounds that selectively bind to and activate ADENOSINE A2 RECEPTORS.Purinergic Antagonists: Drugs that bind to and block the activation of PURINERGIC RECEPTORS.