Purinergic P1 Receptor Agonists: Compounds that bind to and stimulate PURINERGIC P1 RECEPTORS.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.Dopamine Agonists: Drugs that bind to and activate dopamine receptors.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.Serotonin 5-HT2 Receptor Agonists: Endogenous compounds and drugs that specifically stimulate SEROTONIN 5-HT2 RECEPTORS. Included under this heading are agonists for one or more of the specific 5-HT2 receptor subtypes.Adenosine A1 Receptor Agonists: Compounds that bind to and stimulate ADENOSINE A1 RECEPTORS.GABA Agonists: Endogenous compounds and drugs that bind to and activate GAMMA-AMINOBUTYRIC ACID receptors (RECEPTORS, GABA).Adenosine A2 Receptor Agonists: Compounds that selectively bind to and activate ADENOSINE A2 RECEPTORS.Interleukin-1beta: An interleukin-1 subtype that is synthesized as an inactive membrane-bound pro-protein. Proteolytic processing of the precursor form by CASPASE 1 results in release of the active form of interleukin-1beta from the membrane.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.GABA-A Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-A RECEPTORS.GABA-B Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-B RECEPTORS.Cannabinoid Receptor Agonists: Compounds that interact with and stimulate the activity of CANNABINOID RECEPTORS.Serotonin 5-HT4 Receptor Agonists: Endogenous compounds and drugs that specifically stimulate SEROTONIN 5-HT4 RECEPTORS.Purinergic P2 Receptor Agonists: Compounds that bind to and stimulate PURINERGIC P2 RECEPTORS.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.Adrenergic alpha-2 Receptor Agonists: Compounds that bind to and activate ADRENERGIC ALPHA-2 RECEPTORS.Receptors, Adrenergic, beta: One of two major pharmacologically defined classes of adrenergic receptors. The beta adrenergic receptors play an important role in regulating CARDIAC MUSCLE contraction, SMOOTH MUSCLE relaxation, and GLYCOGENOLYSIS.Receptors, Opioid, kappa: A class of opioid receptors recognized by its pharmacological profile. Kappa opioid receptors bind dynorphins with a higher affinity than endorphins which are themselves preferred to enkephalins.Adenosine A3 Receptor Agonists: Drugs that selectively bind to and activate ADENOSINE A3 RECEPTORS.Histamine Agonists: Drugs that bind to and activate histamine receptors. Although they have been suggested for a variety of clinical applications histamine agonists have so far been more widely used in research than therapeutically.beta 2-Microglobulin: An 11-kDa protein associated with the outer membrane of many cells including lymphocytes. It is the small subunit of the MHC class I molecule. Association with beta 2-microglobulin is generally required for the transport of class I heavy chains from the endoplasmic reticulum to the cell surface. Beta 2-microglobulin is present in small amounts in serum, csf, and urine of normal people, and to a much greater degree in the urine and plasma of patients with tubular proteinemia, renal failure, or kidney transplants.Adrenergic beta-3 Receptor Agonists: Compounds that bind to and activate ADRENERGIC BETA-3 RECEPTORS.Muscarinic Agonists: Drugs that bind to and activate muscarinic cholinergic receptors (RECEPTORS, MUSCARINIC). Muscarinic agonists are most commonly used when it is desirable to increase smooth muscle tone, especially in the GI tract, urinary bladder and the eye. They may also be used to reduce heart rate.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.Adrenergic beta-Agonists: Drugs that selectively bind to and activate beta-adrenergic receptors.Receptors, 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.Nicotinic Agonists: Drugs that bind to and activate nicotinic cholinergic receptors (RECEPTORS, NICOTINIC). Nicotinic agonists act at postganglionic nicotinic receptors, at neuroeffector junctions in the peripheral nervous system, and at nicotinic receptors in the central nervous system. Agents that function as neuromuscular depolarizing blocking agents are included here because they activate nicotinic receptors, although they are used clinically to block nicotinic transmission.Serotonin Antagonists: Drugs that bind to but do not activate serotonin receptors, thereby blocking the actions of serotonin or SEROTONIN RECEPTOR AGONISTS.Adrenergic Agonists: Drugs that bind to and activate adrenergic receptors.2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine: A selective D1 dopamine receptor agonist used primarily as a research tool.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.Phenethylamines: A group of compounds that are derivatives of beta- aminoethylbenzene which is structurally and pharmacologically related to amphetamine. (From Merck Index, 11th ed)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.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.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).Receptors, Opioid, delta: A class of opioid receptors recognized by its pharmacological profile. Delta opioid receptors bind endorphins and enkephalins with approximately equal affinity and have less affinity for dynorphins.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.Quinpirole: A dopamine D2/D3 receptor agonist.Excitatory Amino Acid Agonists: Drugs that bind to and activate excitatory amino acid receptors.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.Integrin beta3: An integrin beta subunit of approximately 85-kDa in size which has been found in INTEGRIN ALPHAIIB-containing and INTEGRIN ALPHAV-containing heterodimers. Integrin beta3 occurs as three alternatively spliced isoforms, designated beta3A-C.Piperidines: A family of hexahydropyridines.Benzazepines: Compounds with BENZENE fused to AZEPINES.8-Hydroxy-2-(di-n-propylamino)tetralin: A serotonin 1A-receptor agonist that is used experimentally to test the effects of serotonin.Enkephalin, Ala(2)-MePhe(4)-Gly(5)-: An enkephalin analog that selectively binds to the MU OPIOID RECEPTOR. It is used as a model for drug permeability experiments.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.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, Adrenergic, beta-2: A subclass of beta-adrenergic receptors (RECEPTORS, ADRENERGIC, BETA). The adrenergic beta-2 receptors are more sensitive to EPINEPHRINE than to NOREPINEPHRINE and have a high affinity for the agonist TERBUTALINE. They are widespread, with clinically important roles in SKELETAL MUSCLE; LIVER; and vascular, bronchial, gastrointestinal, and genitourinary SMOOTH MUSCLE.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).Adrenergic alpha-1 Receptor Agonists: Compounds that bind to and activate ADRENERGIC ALPHA-1 RECEPTORS.Cannabinoids: Compounds having the cannabinoid structure. They were originally extracted from Cannabis sativa L. The most pharmacologically active constituents are TETRAHYDROCANNABINOL; CANNABINOL; and CANNABIDIOL.Adrenergic alpha-Agonists: Drugs that selectively bind to and activate alpha adrenergic receptors.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.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.PyrrolidinesNaphthalenes: Two-ring crystalline hydrocarbons isolated from coal tar. They are used as intermediates in chemical synthesis, as insect repellents, fungicides, lubricants, preservatives, and, formerly, as topical antiseptics.Cell Line: Established cell cultures that have the potential to propagate indefinitely.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.Adenosine-5'-(N-ethylcarboxamide): A stable adenosine A1 and A2 receptor agonist. Experimentally, it inhibits cAMP and cGMP phosphodiesterase activity.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.Ligands: A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)Receptors, Glucagon: Cell surface receptors that bind glucagon with high affinity and trigger intracellular changes which influence the behavior of cells. Activation of glucagon receptors causes a variety of effects; the best understood is the initiation of a complex enzymatic cascade in the liver which ultimately increases the availability of glucose to body organs.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.Enkephalin, D-Penicillamine (2,5)-: A disulfide opioid pentapeptide that selectively binds to the DELTA OPIOID RECEPTOR. It possesses antinociceptive activity.Cholinergic Agonists: Drugs that bind to and activate cholinergic receptors.Drug Interactions: The action of a drug that may affect the activity, metabolism, or toxicity of another drug.Benzoxazines: OXAZINES with a fused BENZENE ring.Purinergic P1 Receptor Antagonists: Compounds that bind to and block the stimulation of PURINERGIC P1 RECEPTORS.Mice, Inbred C57BLRNA, 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.Receptor, Cannabinoid, CB2: A subclass of cannabinoid receptor found primarily on immune cells where it may play a role modulating release of CYTOKINES.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.Venoms: Poisonous animal secretions forming fluid mixtures of many different enzymes, toxins, and other substances. These substances are produced in specialized glands and secreted through specialized delivery systems (nematocysts, spines, fangs, etc.) for disabling prey or predator.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.Serotonin 5-HT3 Receptor Agonists: Endogenous compounds and drugs that specifically stimulate SEROTONIN 5-HT3 RECEPTORS.Transforming Growth Factor beta: A factor synthesized in a wide variety of tissues. It acts synergistically with TGF-alpha in inducing phenotypic transformation and can also act as a negative autocrine growth factor. TGF-beta has a potential role in embryonal development, cellular differentiation, hormone secretion, and immune function. TGF-beta is found mostly as homodimer forms of separate gene products TGF-beta1, TGF-beta2 or TGF-beta3. Heterodimers composed of TGF-beta1 and 2 (TGF-beta1.2) or of TGF-beta2 and 3 (TGF-beta2.3) have been isolated. The TGF-beta proteins are synthesized as precursor proteins.Receptor, Cannabinoid, CB1: A subclass of cannabinoid receptor found primarily on central and peripheral NEURONS where it may play a role modulating NEUROTRANSMITTER release.Tetrahydronaphthalenes: Partially saturated 1,2,3,4-tetrahydronaphthalene compounds.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.Purinergic P2X Receptor Agonists: Compounds that bind to and stimulate PURINERGIC P2X RECEPTORS. Included under this heading are agonists for specific P2X receptor subtypes.Pyridines: Compounds with a six membered aromatic ring containing NITROGEN. The saturated version is PIPERIDINES.Purinergic P2Y Receptor Agonists: Compounds that bind to and stimulate PURINERGIC P2Y RECEPTORS. Included under this heading are agonists for specific P2Y receptor subtypes.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.Behavior, Animal: The observable response an animal makes to any situation.Apomorphine: A derivative of morphine that is a dopamine D2 agonist. It is a powerful emetic and has been used for that effect in acute poisoning. It has also been used in the diagnosis and treatment of parkinsonism, but its adverse effects limit its use.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.Sumatriptan: A serotonin agonist that acts selectively at 5HT1 receptors. It is used in the treatment of MIGRAINE DISORDERS.Isoproterenol: Isopropyl analog of EPINEPHRINE; beta-sympathomimetic that acts on the heart, bronchi, skeletal muscle, alimentary tract, etc. It is used mainly as bronchodilator and heart stimulant.Receptors, Dopamine D3: A subtype of dopamine D2 receptors that are highly expressed in the LIMBIC SYSTEM of the brain.Ergolines: A series of structurally-related alkaloids that contain the ergoline backbone structure.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.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.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.Methylhistamines: Histamine substituted in any position with one or more methyl groups. Many of these are agonists for the H1, H2, or both histamine receptors.Benzeneacetamides: Compounds based on benzeneacetamide, that are similar in structure to ACETANILIDES.Xanthines: Purine bases found in body tissues and fluids and in some plants.PiperazinesMorpholinesReceptors, 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.Bicyclo Compounds, Heterocyclic: A class of saturated compounds consisting of two rings only, having two or more atoms in common, containing at least one hetero atom, and that take the name of an open chain hydrocarbon containing the same total number of atoms. (From Riguady et al., Nomenclature of Organic Chemistry, 1979, p31)Receptors, sigma: A class of cell surface receptors recognized by its pharmacological profile. Sigma receptors were originally considered to be opioid receptors because they bind certain synthetic opioids. However they also interact with a variety of other psychoactive drugs, and their endogenous ligand is not known (although they can react to certain endogenous steroids). Sigma receptors are found in the immune, endocrine, and nervous systems, and in some peripheral tissues.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Enkephalins: One of the three major families of endogenous opioid peptides. The enkephalins are pentapeptides that are widespread in the central and peripheral nervous systems and in the adrenal medulla.Adrenergic beta-2 Receptor Agonists: Compounds bind to and activate ADRENERGIC BETA-2 RECEPTORS.Narcotic Antagonists: Agents inhibiting the effect of narcotics on the central nervous system.Receptors, Adrenergic, beta-1: A subclass of beta-adrenergic receptors (RECEPTORS, ADRENERGIC, BETA). The adrenergic beta-1 receptors are equally sensitive to EPINEPHRINE and NOREPINEPHRINE and bind the agonist DOBUTAMINE and the antagonist METOPROLOL with high affinity. They are found in the HEART, juxtaglomerular cells, and in the central and peripheral nervous systems.Receptors, Prostaglandin E: Cell surface receptors which bind prostaglandins with a high affinity and trigger intracellular changes which influence the behavior of cells. Prostaglandin E receptors prefer prostaglandin E2 to other endogenous prostaglandins. They are subdivided into EP1, EP2, and EP3 types based on their effects and their pharmacology.Receptor, Serotonin, 5-HT1A: A serotonin receptor subtype found distributed through the CENTRAL NERVOUS SYSTEM where they are involved in neuroendocrine regulation of ACTH secretion. The fact that this serotonin receptor subtype is particularly sensitive to SEROTONIN RECEPTOR AGONISTS such as BUSPIRONE suggests its role in the modulation of ANXIETY and DEPRESSION.Receptor, Adenosine A3: A subtype of ADENOSINE RECEPTOR that is found expressed in a variety of locations including the BRAIN and endocrine tissues. The receptor is generally considered to be coupled to the GI, INHIBITORY G-PROTEIN which causes down regulation of CYCLIC AMP.Receptor, Adenosine A1: A subtype of ADENOSINE RECEPTOR that is found expressed in a variety of tissues including the BRAIN and DORSAL HORN NEURONS. The receptor is generally considered to be coupled to the GI, INHIBITORY G-PROTEIN which causes down regulation of CYCLIC AMP.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.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.Receptors, Adrenergic, beta-3: A subclass of beta-adrenergic receptors (RECEPTORS, ADRENERGIC, BETA). The beta-3 adrenergic receptors are the predominant beta-adrenergic receptor type expressed in white and brown ADIPOCYTES and are involved in modulating ENERGY METABOLISM and THERMOGENESIS.Bicyclo CompoundsKinetics: The rate dynamics in chemical or physical systems.Receptors, GABA-B: A subset of GABA RECEPTORS that signal through their interaction with HETEROTRIMERIC G-PROTEINS.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.Motor Activity: The physical activity of a human or an animal as a behavioral phenomenon.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.Oligopeptides: Peptides composed of between two and twelve amino acids.Carbachol: A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS.Receptors, Histamine: Cell-surface proteins that bind histamine and trigger intracellular changes influencing the behavior of cells. Histamine receptors are widespread in the central nervous system and in peripheral tissues. Three types have been recognized and designated H1, H2, and H3. They differ in pharmacology, distribution, and mode of action.Integrin alpha5beta1: An integrin found in FIBROBLASTS; PLATELETS; MONOCYTES, and LYMPHOCYTES. Integrin alpha5beta1 is the classical receptor for FIBRONECTIN, but it also functions as a receptor for LAMININ and several other EXTRACELLULAR MATRIX PROTEINS.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)Receptors, Metabotropic Glutamate: Cell surface proteins that bind glutamate and act through G-proteins to influence second messenger systems. Several types of metabotropic glutamate receptors have been cloned. They differ in pharmacology, distribution, and mechanisms of action.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.Receptors, Nicotinic: One of the two major classes of cholinergic receptors. Nicotinic receptors were originally distinguished by their preference for NICOTINE over MUSCARINE. They are generally divided into muscle-type and neuronal-type (previously ganglionic) based on pharmacology, and subunit composition of the receptors.Integrin beta4: Also known as CD104 antigen, this protein is distinguished from other beta integrins by its relatively long cytoplasmic domain (approximately 1000 amino acids vs. approximately 50). Five alternatively spliced isoforms have been described.Receptors, Dopamine: Cell-surface proteins that bind dopamine with high affinity and trigger intracellular changes influencing the behavior of cells.Purinergic Agonists: Compounds that bind to and activate PURINERGIC RECEPTORS.GTP-Binding Proteins: Regulatory proteins that act as molecular switches. They control a wide range of biological processes including: receptor signaling, intracellular signal transduction pathways, and protein synthesis. Their activity is regulated by factors that control their ability to bind to and hydrolyze GTP to GDP. EC 3.6.1.-.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Propanolamines: AMINO ALCOHOLS containing the propanolamine (NH2CH2CHOHCH2) group and its derivatives.Guanosine 5'-O-(3-Thiotriphosphate): Guanosine 5'-(trihydrogen diphosphate), monoanhydride with phosphorothioic acid. A stable GTP analog which enjoys a variety of physiological actions such as stimulation of guanine nucleotide-binding proteins, phosphoinositide hydrolysis, cyclic AMP accumulation, and activation of specific proto-oncogenes.Fenoldopam: A dopamine D1 receptor agonist that is used as an antihypertensive agent. It lowers blood pressure through arteriolar vasodilation.Integrin alpha6beta4: This intrgrin is a key component of HEMIDESMOSOMES and is required for their formation and maintenance in epithelial cells. Integrin alpha6beta4 is also found on thymocytes, fibroblasts, and Schwann cells, where it functions as a laminin receptor (RECEPTORS, LAMININ) and is involved in wound healing, cell migration, and tumor invasiveness.Dopamine Agents: Any drugs that are used for their effects on dopamine receptors, on the life cycle of dopamine, or on the survival of dopaminergic neurons.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.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Hydrocarbons, FluorinatedClonidine: An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.Receptors, Purinergic P2: A class of cell surface receptors for PURINES that prefer ATP or ADP over ADENOSINE. P2 purinergic receptors are widespread in the periphery and in the central and peripheral nervous system.Integrin beta Chains: Integrin beta chains combine with integrin alpha chains to form heterodimeric cell surface receptors. Integrins have traditionally been classified into functional groups based on the identity of one of three beta chains present in the heterodimer. The beta chain is necessary and sufficient for integrin-dependent signaling. Its short cytoplasmic tail contains sequences critical for inside-out signaling.beta 2-Glycoprotein I: A 44-kDa highly glycosylated plasma protein that binds phospholipids including CARDIOLIPIN; APOLIPOPROTEIN E RECEPTOR; membrane phospholipids, and other anionic phospholipid-containing moieties. It plays a role in coagulation and apoptotic processes. Formerly known as apolipoprotein H, it is an autoantigen in patients with ANTIPHOSPHOLIPID ANTIBODIES.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.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Impromidine: A highly potent and specific histamine H2 receptor agonist. It has been used diagnostically as a gastric secretion indicator.Peptide Fragments: Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.Receptor, 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.Receptors, Purinergic: Cell surface proteins that bind PURINES with high affinity and trigger intracellular changes which influence the behavior of cells. The best characterized classes of purinergic receptors in mammals are the P1 receptors, which prefer ADENOSINE, and the P2 receptors, which prefer ATP or ADP.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.Amphetamines: Analogs or derivatives of AMPHETAMINE. Many are sympathomimetics and central nervous system stimulators causing excitation, vasopressin, bronchodilation, and to varying degrees, anorexia, analepsis, nasal decongestion, and some smooth muscle relaxation.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).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.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Receptors, Histamine H2: A class of histamine receptors discriminated by their pharmacology and mode of action. Histamine H2 receptors act via G-proteins to stimulate ADENYLYL CYCLASES. Among the many responses mediated by these receptors are gastric acid secretion, smooth muscle relaxation, inotropic and chronotropic effects on heart muscle, and inhibition of lymphocyte function. (From Biochem Soc Trans 1992 Feb;20(1):122-5)Naloxone: A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Receptors, Drug: Proteins that bind specific drugs with high affinity and trigger intracellular changes influencing the behavior of cells. Drug receptors are generally thought to be receptors for some endogenous substance not otherwise specified.Integrin alpha4beta1: Integrin alpha4beta1 is a FIBRONECTIN and VCAM-1 receptor present on LYMPHOCYTES; MONOCYTES; EOSINOPHILS; NK CELLS and thymocytes. It is involved in both cell-cell and cell- EXTRACELLULAR MATRIX adhesion and plays a role in INFLAMMATION, hematopoietic cell homing and immune function, and has been implicated in skeletal MYOGENESIS; NEURAL CREST migration and proliferation, lymphocyte maturation and morphogenesis of the PLACENTA and HEART.QuinoxalinesEstrogen Receptor beta: One of the ESTROGEN RECEPTORS that has greater affinity for ISOFLAVONES than ESTROGEN RECEPTOR ALPHA does. There is great sequence homology with ER alpha in the DNA-binding domain but not in the ligand binding and hinge domains.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Cyclohexanols: Monohydroxy derivatives of cyclohexanes that contain the general formula R-C6H11O. They have a camphorlike odor and are used in making soaps, insecticides, germicides, dry cleaning, and plasticizers.Electric Stimulation: Use of electric potential or currents to elicit biological responses.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.Receptors, Adrenergic, alpha-2: A subclass of alpha-adrenergic receptors found on both presynaptic and postsynaptic membranes where they signal through Gi-Go G-PROTEINS. While postsynaptic alpha-2 receptors play a traditional role in mediating the effects of ADRENERGIC AGONISTS, the subset of alpha-2 receptors found on presynaptic membranes signal the feedback inhibition of NEUROTRANSMITTER release.Muscle, Smooth: Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)Morphinans: Compounds based on a partially saturated iminoethanophenanthrene, which can be described as ethylimino-bridged benzo-decahydronaphthalenes. They include some of the OPIOIDS found in PAPAVER that are used as ANALGESICS.Integrin alpha2beta1: An integrin found on fibroblasts, platelets, endothelial and epithelial cells, and lymphocytes where it functions as a receptor for COLLAGEN and LAMININ. Although originally referred to as the collagen receptor, it is one of several receptors for collagen. Ligand binding to integrin alpha2beta1 triggers a cascade of intracellular signaling, including activation of p38 MAP kinase.Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Structure-Activity Relationship: The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.Receptors, 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.Dronabinol: A psychoactive compound extracted from the resin of Cannabis sativa (marihuana, hashish). The isomer delta-9-tetrahydrocannabinol (THC) is considered the most active form, producing characteristic mood and perceptual changes associated with this compound.Adenosine A2 Receptor Antagonists: Compounds that selectively bind to and block the activation of ADENOSINE A2 RECEPTORS.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.Receptors, Muscarinic: One of the two major classes of cholinergic receptors. Muscarinic receptors were originally defined by their preference for MUSCARINE over NICOTINE. There are several subtypes (usually M1, M2, M3....) that are characterized by their cellular actions, pharmacology, and molecular biology.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.Colforsin: Potent activator of the adenylate cyclase system and the biosynthesis of cyclic AMP. From the plant COLEUS FORSKOHLII. Has antihypertensive, positive inotropic, platelet aggregation inhibitory, and smooth muscle relaxant activities; also lowers intraocular pressure and promotes release of hormones from the pituitary gland.Receptors, 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.Receptors, Neuropeptide Y: Cell surface proteins that bind neuropeptide Y with high affinity and trigger intracellular changes which influence the behavior of cells.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.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.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.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.Adenosine A1 Receptor Antagonists: Compounds that bind to and block the stimulation of ADENOSINE A1 RECEPTORS.Synaptic 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.Dimaprit: A histamine H2 receptor agonist that is often used to study the activity of histamine and its receptors.Benzylidene Compounds: Compounds containing the PhCH= radical.Sulfonamides: A group of compounds that contain the structure SO2NH2.Receptors, Cannabinoid: A class of G-protein-coupled receptors that are specific for CANNABINOIDS such as those derived from CANNABIS. They also bind a structurally distinct class of endogenous factors referred to as ENDOCANNABINOIDS. The receptor class may play a role in modulating the release of signaling molecules such as NEUROTRANSMITTERS and CYTOKINES.Injections, Intraventricular: Injections into the cerebral ventricles.Adrenergic beta-Antagonists: Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety.Phenylisopropyladenosine: N-Isopropyl-N-phenyl-adenosine. Antilipemic agent. Synonym: TH 162.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).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.Benzomorphans: Morphine derivatives of the methanobenzazocine family that act as potent analgesics.N-Methylaspartate: An amino acid that, as the D-isomer, is the defining agonist for the NMDA receptor subtype of glutamate receptors (RECEPTORS, NMDA).