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.

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.

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.

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.

Compounds with activity like OPIATE ALKALOIDS, acting at OPIOID RECEPTORS. Properties include induction of ANALGESIA or NARCOSIS.

Agents inhibiting the effect of narcotics on the central nervous system.

The endogenous peptides with opiate-like activity. The three major classes currently recognized are the ENKEPHALINS, the DYNORPHINS, and the ENDORPHINS. Each of these families derives from different precursors, proenkephalin, prodynorphin, and PRO-OPIOMELANOCORTIN, respectively. There are also at least three classes of OPIOID RECEPTORS, but the peptide families do not map to the receptors in a simple way.

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.

A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.

An enkephalin analog that selectively binds to the MU OPIOID RECEPTOR. It is used as a model for drug permeability experiments.

A disulfide opioid pentapeptide that selectively binds to the DELTA OPIOID RECEPTOR. It possesses antinociceptive activity.

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.

A narcotic antagonist similar in action to NALOXONE. It is used to remobilize animals after ETORPHINE neuroleptanalgesia and is considered a specific antagonist to etorphine.

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.

A class of opioid peptides including dynorphin A, dynorphin B, and smaller fragments of these peptides. Dynorphins prefer kappa-opioid receptors (RECEPTORS, OPIOID, KAPPA) and have been shown to play a role as central nervous system transmitters.

A delta-selective opioid (ANALGESICS, OPIOID). It can cause transient depression of mean arterial blood pressure and heart rate.

One of the endogenous pentapeptides with morphine-like activity. It differs from MET-ENKEPHALIN in the LEUCINE at position 5. Its first four amino acid sequence is identical to the tetrapeptide sequence at the N-terminal of BETA-ENDORPHIN.

Compounds based on benzeneacetamide, that are similar in structure to ACETANILIDES.

Agents that induce NARCOSIS. Narcotics include agents that cause somnolence or induced sleep (STUPOR); natural or synthetic derivatives of OPIUM or MORPHINE or any substance that has such effects. They are potent inducers of ANALGESIA and OPIOID-RELATED DISORDERS.

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.

Morphine derivatives of the methanobenzazocine family that act as potent analgesics.

Compounds capable of relieving pain without the loss of CONSCIOUSNESS.

One of the three major groups of endogenous opioid peptides. They are large peptides derived from the PRO-OPIOMELANOCORTIN precursor. The known members of this group are alpha-, beta-, and gamma-endorphin. The term endorphin is also sometimes used to refer to all opioid peptides, but the narrower sense is used here; OPIOID PEPTIDES is used for the broader group.

A narcotic analgesic morphinan used as a sedative in veterinary practice.

A 31-amino acid peptide that is the C-terminal fragment of BETA-LIPOTROPIN. It acts on OPIOID RECEPTORS and is an analgesic. Its first four amino acids at the N-terminal are identical to the tetrapeptide sequence of METHIONINE ENKEPHALIN and LEUCINE ENKEPHALIN.

Pyrrolidines are saturated, heterocyclic organic compounds containing a five-membered ring with four carbon atoms and one nitrogen atom (NRCH2CH2), commonly found as structural components in various alkaloids and used in the synthesis of pharmaceuticals and other organic materials.

A group of DITERPENES cyclized into 2-rings with a side-chain.

Disorders related or resulting from abuse or mis-use of opioids.

A kappa opioid receptor agonist. The compound has analgesic action and shows positive inotropic effects on the electrically stimulated left atrium. It also affects various types of behavior in mammals such as locomotion, rearing, and grooming.

An analgesic with mixed narcotic agonist-antagonist properties.

Compounds containing the PhCH= radical.

Progressive diminution of the susceptibility of a human or animal to the effects of a drug, resulting from its continued administration. It should be differentiated from DRUG RESISTANCE wherein an organism, disease, or tissue fails to respond to the intended effectiveness of a chemical or drug. It should also be differentiated from MAXIMUM TOLERATED DOSE and NO-OBSERVED-ADVERSE-EFFECT LEVEL.

A narcotic analgesic that may be habit-forming. It is nearly as effective orally as by injection.

An unpleasant sensation induced by noxious stimuli which are detected by NERVE ENDINGS of NOCICEPTIVE NEURONS.

A potent narcotic analgesic, abuse of which leads to habituation or addiction. It is primarily a mu-opioid agonist. Fentanyl is also used as an adjunct to general anesthetics, and as an anesthetic for induction and maintenance. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1078)

Scales, questionnaires, tests, and other methods used to assess pain severity and duration in patients or experimental animals to aid in diagnosis, therapy, and physiological studies.

A derivative of the opioid alkaloid THEBAINE that is a more potent and longer lasting analgesic than MORPHINE. It appears to act as a partial agonist at mu and kappa opioid receptors and as an antagonist at delta receptors. The lack of delta-agonist activity has been suggested to account for the observation that buprenorphine tolerance may not develop with chronic use.

One of the endogenous pentapeptides with morphine-like activity. It differs from LEU-ENKEPHALIN by the amino acid METHIONINE in position 5. Its first four amino acid sequence is identical to the tetrapeptide sequence at the N-terminal of BETA-ENDORPHIN.

Methods of PAIN relief that may be used with or in place of ANALGESICS.

Peptides composed of between two and twelve amino acids.

Analogs or derivatives of morphine.

A synthetic morphinan analgesic with narcotic antagonist action. It is used in the management of severe pain.

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.

The relationship between the dose of an administered drug and the response of the organism to the drug.

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.

A narcotic analgesic that may be habit-forming. It is a controlled substance (opium derivative) listed in the U.S. Code of Federal Regulations, Title 21 Parts 329.1, 1308.11 (1987). Sale is forbidden in the United States by Federal statute. (Merck Index, 11th ed)

Physiological and psychological symptoms associated with withdrawal from the use of a drug after prolonged administration or habituation. The concept includes withdrawal from smoking or drinking, as well as withdrawal from an administered drug.

Strong dependence, both physiological and emotional, upon morphine.

Introduction of therapeutic agents into the spinal region using a needle and syringe.

Quantitative determination of receptor (binding) proteins in body fluids or tissue using radioactively labeled binding reagents (e.g., antibodies, intracellular receptors, plasma binders).

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)

Central gray matter surrounding the CEREBRAL AQUEDUCT in the MESENCEPHALON. Physiologically it is probably involved in RAGE reactions, the LORDOSIS REFLEX; FEEDING responses, bladder tonus, and pain.

A synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. It has actions and uses similar to those of MORPHINE. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1082-3)

One of the long-acting synthetic ANTIDIARRHEALS; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally.

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.

A 14-amino acid peptide named for its ability to inhibit pituitary GROWTH HORMONE release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of THYROID-STIMULATING HORMONE; PROLACTIN; INSULIN; and GLUCAGON besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, SRIF-28 with a 14-amino acid extension at the N-terminal.

An increased sensation of pain or discomfort produced by mimimally noxious stimuli due to damage to soft tissue containing NOCICEPTORS or injury to a peripheral nerve.

Amount of stimulation required before the sensation of pain is experienced.

Peripheral AFFERENT NEURONS which are sensitive to injuries or pain, usually caused by extreme thermal exposures, mechanical forces, or other noxious stimuli. Their cell bodies reside in the DORSAL ROOT GANGLIA. Their peripheral terminals (NERVE ENDINGS) innervate target tissues and transduce noxious stimuli via axons to the CENTRAL NERVOUS SYSTEM.

A subclass of analgesic agents that typically do not bind to OPIOID RECEPTORS and are not addictive. Many non-narcotic analgesics are offered as NONPRESCRIPTION DRUGS.

Alkaloids found in OPIUM from PAPAVER that induce analgesic and narcotic effects by action upon OPIOID RECEPTORS.

A genus in the mint family (LAMIACEAE).

A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.

An opioid analgesic made from MORPHINE and used mainly as an analgesic. It has a shorter duration of action than morphine.

Injections into the cerebral ventricles.

A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.

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.

A genus of the family Muridae consisting of eleven species. C. migratorius, the grey or Armenian hamster, and C. griseus, the Chinese hamster, are the two species used in biomedical research.

A stable synthetic analog of methionine enkephalin (ENKEPHALIN, METHIONINE). Actions are similar to those of methionine enkephalin. Its effects can be reversed by narcotic antagonists such as naloxone.

Azocines are a class of heterocyclic organic compounds containing a seven-membered ring with two nitrogen atoms connected by an azo group (-N=N-) in the 1,3-positions.

A group of compounds consisting in part of two rings sharing one atom (usually a carbon) in common.

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.

The observable response an animal makes to any situation.

A ubiquitously expressed G-protein-coupled receptor kinase subtype that has specificity for the agonist-occupied form of BETA-ADRENERGIC RECEPTORS and a variety of other G-PROTEIN-COUPLED RECEPTORS. Although it is highly homologous to G-PROTEIN-COUPLED RECEPTOR KINASE 2, it is not considered to play an essential role in regulating myocardial contractile response.

The action of a drug that may affect the activity, metabolism, or toxicity of another drug.

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.

A semisynthetic analgesic used in the study of narcotic receptors.

Regulatory proteins that down-regulate phosphorylated G-protein membrane receptors, including rod and cone photoreceptors and adrenergic receptors.

Strong dependence, both physiological and emotional, upon heroin.

A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.

A family of hexahydropyridines.

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.-.

The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.

A narcotic used as a pain medication. It appears to be an agonist at kappa opioid receptors and an antagonist or partial agonist at mu opioid receptors.

A narcotic analgesic proposed for severe pain. It may be habituating.

The excretory duct of the testes that carries SPERMATOZOA. It rises from the SCROTUM and joins the SEMINAL VESICLES to form the ejaculatory duct.

Sensing of noxious mechanical, thermal or chemical stimuli by NOCICEPTORS. It is the sensory component of visceral and tissue pain (NOCICEPTIVE PAIN).

Collection of pleomorphic cells in the caudal part of the anterior horn of the LATERAL VENTRICLE, in the region of the OLFACTORY TUBERCLE, lying between the head of the CAUDATE NUCLEUS and the ANTERIOR PERFORATED SUBSTANCE. It is part of the so-called VENTRAL STRIATUM, a composite structure considered part of the BASAL GANGLIA.

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.

An enzyme of the lyase class that catalyzes the formation of CYCLIC AMP and pyrophosphate from ATP. EC 4.6.1.1.

The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.

A form of acupuncture with electrical impulses passing through the needles to stimulate NERVE TISSUE. It can be used for ANALGESIA; ANESTHESIA; REHABILITATION; and treatment for diseases.

Aching sensation that persists for more than a few months. It may or may not be associated with trauma or disease, and may persist after the initial injury has healed. Its localization, character, and timing are more vague than with acute pain.

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.

The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)

An opioid analgesic with actions and uses similar to those of MORPHINE, apart from an absence of cough suppressant activity. It is used in the treatment of moderate to severe pain, including pain in obstetrics. It may also be used as an adjunct to anesthesia. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1092)

Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced.

One of the virulence factors produced by BORDETELLA PERTUSSIS. It is a multimeric protein composed of five subunits S1 - S5. S1 contains mono ADPribose transferase activity.

A group of ISOQUINOLINES in which the nitrogen containing ring is protonated. They derive from the non-enzymatic Pictet-Spengler condensation of CATECHOLAMINES with ALDEHYDES.

BENZOIC ACID amides.

Inbred ICR mice are a strain of albino laboratory mice that have been selectively bred for consistent genetic makeup and high reproductive performance, making them widely used in biomedical research for studies involving reproduction, toxicology, pharmacology, and carcinogenesis.

Administration of a drug or chemical by the individual under the direction of a physician. It includes administration clinically or experimentally, by human or animal.

Established cell cultures that have the potential to propagate indefinitely.

Narcotic analgesic related to CODEINE, but more potent and more addicting by weight. It is used also as cough suppressant.

A narcotic antagonist with analgesic properties. It is used for the control of moderate to severe pain.

An opioid analgesic with actions and uses similar to MORPHINE. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1095)

Piperazines are a class of heterocyclic organic compounds containing a seven-membered ring with two nitrogen atoms at positions 1 and 4, often used in pharmaceuticals as smooth muscle relaxants, antipsychotics, antidepressants, and antihistamines, but can also be found as recreational drugs with stimulant and entactogen properties.

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.

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.

The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.

Protein precursors, also known as proproteins or prohormones, are inactive forms of proteins that undergo post-translational modification, such as cleavage, to produce the active functional protein or peptide hormone.

A clear, colorless liquid rapidly absorbed from the gastrointestinal tract and distributed throughout the body. It has bactericidal activity and is used often as a topical disinfectant. It is widely used as a solvent and preservative in pharmaceutical preparations as well as serving as the primary ingredient in ALCOHOLIC BEVERAGES.

The physical activity of a human or an animal as a behavioral phenomenon.

An antigen solution emulsified in mineral oil. The complete form is made up of killed, dried mycobacteria, usually M. tuberculosis, suspended in the oil phase. It is effective in stimulating cell-mediated immunity (IMMUNITY, CELLULAR) and potentiates the production of certain IMMUNOGLOBULINS in some animals. The incomplete form does not contain mycobacteria.

Use of electric potential or currents to elicit biological responses.

Medical treatment for opioid dependence using a substitute opiate such as METHADONE or BUPRENORPHINE.

Changes in the amounts of various chemicals (neurotransmitters, receptors, enzymes, and other metabolites) specific to the area of the central nervous system contained within the head. These are monitored over time, during sensory stimulation, or under different disease states.

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.

Elements of limited time intervals, contributing to particular results or situations.

An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.

An opioid analgesic that is used as an adjunct in anesthesia, in balanced anesthesia, and as a primary anesthetic agent.

Structurally-related alkaloids that contain the cevane carbon backbone.

Bluish-colored region in the superior angle of the FOURTH VENTRICLE floor, corresponding to melanin-like pigmented nerve cells which lie lateral to the PERIAQUEDUCTAL GRAY.

A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.

The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.

Accidental or deliberate use of a medication or street drug in excess of normal dosage.

A highly reactive aldehyde gas formed by oxidation or incomplete combustion of hydrocarbons. In solution, it has a wide range of uses: in the manufacture of resins and textiles, as a disinfectant, and as a laboratory fixative or preservative. Formaldehyde solution (formalin) is considered a hazardous compound, and its vapor toxic. (From Reynolds, Martindale The Extra Pharmacopoeia, 30th ed, p717)

The first mixed agonist-antagonist analgesic to be marketed. It is an agonist at the kappa and sigma opioid receptors and has a weak antagonist action at the mu receptor. (From AMA Drug Evaluations Annual, 1991, p97)

The nervous system outside of the brain and spinal cord. The peripheral nervous system has autonomic and somatic divisions. The autonomic nervous system includes the enteric, parasympathetic, and sympathetic subdivisions. The somatic nervous system includes the cranial and spinal nerves and their ganglia and the peripheral sensory receptors.

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.

A set of BACTERIAL ADHESINS and TOXINS, BIOLOGICAL produced by BORDETELLA organisms that determine the pathogenesis of BORDETELLA INFECTIONS, such as WHOOPING COUGH. They include filamentous hemagglutinin; FIMBRIAE PROTEINS; pertactin; PERTUSSIS TOXIN; ADENYLATE CYCLASE TOXIN; dermonecrotic toxin; tracheal cytotoxin; Bordetella LIPOPOLYSACCHARIDES; and tracheal colonization factor.

The molecular designing of drugs for specific purposes (such as DNA-binding, enzyme inhibition, anti-cancer efficacy, etc.) based on knowledge of molecular properties such as activity of functional groups, molecular geometry, and electronic structure, and also on information cataloged on analogous molecules. Drug design is generally computer-assisted molecular modeling and does not include pharmacokinetics, dosage analysis, or drug administration analysis.

The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.

The various ways of administering a drug or other chemical to a site in a patient or animal from where the chemical is absorbed into the blood and delivered to the target tissue.

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.

The making of a radiograph of an object or tissue by recording on a photographic plate the radiation emitted by radioactive material within the object. (Dorland, 27th ed)

An induced response to threatening stimuli characterized by complete loss of muscle strength.

Improper use of drugs or medications outside the intended purpose, scope, or guidelines for use. This is in contrast to MEDICATION ADHERENCE, and distinguished from DRUG ABUSE, which is a deliberate or willful action.

An activity in which the body is propelled through water by specific movement of the arms and/or the legs. Swimming as propulsion through water by the movement of limbs, tail, or fins of animals is often studied as a form of PHYSICAL EXERTION or endurance.

Compounds with a 5-membered ring of four carbons and an oxygen. They are aromatic heterocycles. The reduced form is tetrahydrofuran.

The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.

Striped GRAY MATTER and WHITE MATTER consisting of the NEOSTRIATUM and paleostriatum (GLOBUS PALLIDUS). It is located in front of and lateral to the THALAMUS in each cerebral hemisphere. The gray substance is made up of the CAUDATE NUCLEUS and the lentiform nucleus (the latter consisting of the GLOBUS PALLIDUS and PUTAMEN). The WHITE MATTER is the INTERNAL CAPSULE.

Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis.

A common neoplasm of early childhood arising from neural crest cells in the sympathetic nervous system, and characterized by diverse clinical behavior, ranging from spontaneous remission to rapid metastatic progression and death. This tumor is the most common intraabdominal malignancy of childhood, but it may also arise from thorax, neck, or rarely occur in the central nervous system. Histologic features include uniform round cells with hyperchromatic nuclei arranged in nests and separated by fibrovascular septa. Neuroblastomas may be associated with the opsoclonus-myoclonus syndrome. (From DeVita et al., Cancer: Principles and Practice of Oncology, 5th ed, pp2099-2101; Curr Opin Oncol 1998 Jan;10(1):43-51)

A very loosely defined group of drugs that tend to reduce the activity of the central nervous system. The major groups included here are ethyl alcohol, anesthetics, hypnotics and sedatives, narcotics, and tranquilizing agents (antipsychotics and antianxiety agents).

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.

Analgesia produced by the insertion of ACUPUNCTURE needles at certain ACUPUNCTURE POINTS on the body. This activates small myelinated nerve fibers in the muscle which transmit impulses to the spinal cord and then activate three centers - the spinal cord, midbrain and pituitary/hypothalamus - to produce analgesia.

An object or a situation that can serve to reinforce a response, to satisfy a motive, or to afford pleasure.

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.

The rate dynamics in chemical or physical systems.

Compounds that are designed to mimic the 3D structure of a natural peptide or protein.

Exposure of myocardial tissue to brief, repeated periods of vascular occlusion in order to render the myocardium resistant to the deleterious effects of ISCHEMIA or REPERFUSION. The period of pre-exposure and the number of times the tissue is exposed to ischemia and reperfusion vary, the average being 3 to 5 minutes.

The air-dried exudate from the unripe seed capsule of the opium poppy, Papaver somniferum, or its variant, P. album. It contains a number of alkaloids, but only a few - MORPHINE; CODEINE; and PAPAVERINE - have clinical significance. Opium has been used as an analgesic, antitussive, antidiarrheal, and antispasmodic.

A form of therapy that employs a coordinated and interdisciplinary approach for easing the suffering and improving the quality of life of those experiencing pain.

Drugs that cannot be sold legally without a prescription.

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.

An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief.

Inbred C57BL mice are a strain of laboratory mice that have been produced by many generations of brother-sister matings, resulting in a high degree of genetic uniformity and homozygosity, making them widely used for biomedical research, including studies on genetics, immunology, cancer, and neuroscience.

Agents, usually topical, that relieve itching (pruritus).

The parts of a macromolecule that directly participate in its specific combination with another molecule.

Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.

Twenty-carbon compounds derived from MEVALONIC ACID or deoxyxylulose phosphate.

A general term referring to the learning of some particular response.

One of two ganglionated neural networks which together form the ENTERIC NERVOUS SYSTEM. The myenteric (Auerbach's) plexus is located between the longitudinal and circular muscle layers of the gut. Its neurons project to the circular muscle, to other myenteric ganglia, to submucosal ganglia, or directly to the epithelium, and play an important role in regulating and patterning gut motility. (From FASEB J 1989;3:127-38)

A family of inwardly-rectifying potassium channels that are activated by PERTUSSIS TOXIN sensitive G-PROTEIN-COUPLED RECEPTORS. GIRK potassium channels are primarily activated by the complex of GTP-BINDING PROTEIN BETA SUBUNITS and GTP-BINDING PROTEIN GAMMA SUBUNITS.

Sensory ganglia located on the dorsal spinal roots within the vertebral column. The spinal ganglion cells are pseudounipolar. The single primary branch bifurcates sending a peripheral process to carry sensory information from the periphery and a central branch which relays that information to the spinal cord or brain.

AMINO ACIDS composed of GLYCINE substituted at the nitrogen rather than the usual carbon position, resulting in the loss of HYDROGEN BONDING donors. Polymers of these compounds are called PEPTOIDS.

The observable, measurable, and often pathological activity of an organism that portrays its inability to overcome a habit resulting in an insatiable craving for a substance or for performing certain acts. The addictive behavior includes the emotional and physical overdependence on the object of habit in increasing amount or frequency.

A cell line generated from human embryonic kidney cells that were transformed with human adenovirus type 5.

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.

Presence of warmth or heat or a temperature notably higher than an accustomed norm.

Unstable isotopes of sulfur that decay or disintegrate spontaneously emitting radiation. S 29-31, 35, 37, and 38 are radioactive sulfur isotopes.

A subtype of dynamin found primarily in the NEURONS of the brain.

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.

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.

Forceful administration under the skin of liquid medication, nutrient, or other fluid through a hollow needle piercing the skin.

Persistent pain that is refractory to some or all forms of treatment.

A narcotic analgesic that can be used for the relief of most types of moderate to severe pain, including postoperative pain and the pain of labor. Prolonged use may lead to dependence of the morphine type; withdrawal symptoms appear more rapidly than with morphine and are of shorter duration.

Neurons in the SPINAL CORD DORSAL HORN whose cell bodies and processes are confined entirely to the CENTRAL NERVOUS SYSTEM. They receive collateral or direct terminations of dorsal root fibers. They send their axons either directly to ANTERIOR HORN CELLS or to the WHITE MATTER ascending and descending longitudinal fibers.

Quinolines are heterocyclic aromatic organic compounds consisting of a two-nitrogened benzene ring fused to a pyridine ring, which have been synthesized and used as building blocks for various medicinal drugs, particularly antibiotics and antimalarials.

Stimulation of the brain, which is self-administered. The stimulation may result in negative or positive reinforcement.

A degenerative disease of the AUTONOMIC NERVOUS SYSTEM that is characterized by idiopathic ORTHOSTATIC HYPOTENSION and a greatly reduced level of CATECHOLAMINES. No other neurological deficits are present.

Disorders related or resulting from use of cocaine.

Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.

A family of heterotrimeric GTP-binding protein alpha subunits that were originally identified by their ability to inhibit ADENYLYL CYCLASES. Members of this family can couple to beta and gamma G-protein subunits that activate POTASSIUM CHANNELS. The Gi-Go part of the name is also spelled Gi/Go.

Intense or aching pain that occurs along the course or distribution of a peripheral or cranial nerve.

Activities performed to obtain licit or illicit substances.

Substances used for their pharmacological actions on any aspect of neurotransmitter systems. Neurotransmitter agents include agonists, antagonists, degradation inhibitors, uptake inhibitors, depleters, precursors, and modulators of receptor function.

Disorders related to substance abuse.

The strengthening of a conditioned response.

A region in the MESENCEPHALON which is dorsomedial to the SUBSTANTIA NIGRA and ventral to the RED NUCLEUS. The mesocortical and mesolimbic dopaminergic systems originate here, including an important projection to the NUCLEUS ACCUMBENS. Overactivity of the cells in this area has been suspected to contribute to the positive symptoms of SCHIZOPHRENIA.