Partial agonism by 3alpha,21-dihydroxy-5beta-pregnan-20-one at the gamma-aminobutyric acidA receptor neurosteroid site. 1997

B G Xue, and E R Whittemore, and C H Park, and R M Woodward, and N C Lan, and K W Gee
Department of Pharmacology, College of Medicine, University of California, Irvine 92697, USA.

3alpha,21-Dihydroxy-5alpha-pregnan-20-one (5alpha-THDOC) and 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-P) have full efficacy as allosteric modulators of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to sites on the gamma-aminobutyric acid (GABA) type A receptor complex (GRC). Relative to 3alpha,5alpha-P and 5alpha-THDOC, 3alpha,21-dihydroxy-5beta-pregnan-20-one (5beta-THDOC) has limited efficacy as an allosteric modulator of [35S]TBPS binding. Interactions between 3alpha,5alpha-P, 5alpha-THDOC and 5beta-THDOC were examined to determine whether these neuroactive steroids share a common site for modulation of the GRC. The concentration-response curves for both 3alpha,5alpha-P and 5alpha-THDOC modulation of [35S]TBPS binding to brain and recombinantly derived GRCs are shifted rightward in the presence of various concentrations of 5beta-THDOC. Similarly, 5beta-THDOC modulates GABA-evoked Cl- currents with low efficacy and inhibits the potentiation of GABA-evoked Cl- currents by 3alpha,5alpha-P. Furthermore, behavioral studies reveal that 5beta-THDOC antagonizes 3alpha,5alpha-P-induced loss of the righting reflex in mice at a dose that has no effect alone. These results represent the first demonstration of antagonist-like actions of a neuroactive steroid on the GRCs at levels ranging from the receptor to animal behavior and suggest the existence of partial agonist neurosteroids.

UI MeSH Term Description Entries
D008297 Male Males
D011963 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. Benzodiazepine-Gaba Receptors,GABA-A Receptors,Receptors, Benzodiazepine,Receptors, Benzodiazepine-GABA,Receptors, Diazepam,Receptors, GABA-Benzodiazepine,Receptors, Muscimol,Benzodiazepine Receptor,Benzodiazepine Receptors,Benzodiazepine-GABA Receptor,Diazepam Receptor,Diazepam Receptors,GABA(A) Receptor,GABA-A Receptor,GABA-A Receptor alpha Subunit,GABA-A Receptor beta Subunit,GABA-A Receptor delta Subunit,GABA-A Receptor epsilon Subunit,GABA-A Receptor gamma Subunit,GABA-A Receptor rho Subunit,GABA-Benzodiazepine Receptor,GABA-Benzodiazepine Receptors,Muscimol Receptor,Muscimol Receptors,delta Subunit, GABA-A Receptor,epsilon Subunit, GABA-A Receptor,gamma-Aminobutyric Acid Subtype A Receptors,Benzodiazepine GABA Receptor,Benzodiazepine Gaba Receptors,GABA A Receptor,GABA A Receptor alpha Subunit,GABA A Receptor beta Subunit,GABA A Receptor delta Subunit,GABA A Receptor epsilon Subunit,GABA A Receptor gamma Subunit,GABA A Receptor rho Subunit,GABA A Receptors,GABA Benzodiazepine Receptor,GABA Benzodiazepine Receptors,Receptor, Benzodiazepine,Receptor, Benzodiazepine-GABA,Receptor, Diazepam,Receptor, GABA-A,Receptor, GABA-Benzodiazepine,Receptor, Muscimol,Receptors, Benzodiazepine GABA,Receptors, GABA A,Receptors, GABA Benzodiazepine,delta Subunit, GABA A Receptor,epsilon Subunit, GABA A Receptor,gamma Aminobutyric Acid Subtype A Receptors
D002540 Cerebral Cortex The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulci. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions. Allocortex,Archipallium,Cortex Cerebri,Cortical Plate,Paleocortex,Periallocortex,Allocortices,Archipalliums,Cerebral Cortices,Cortex Cerebrus,Cortex, Cerebral,Cortical Plates,Paleocortices,Periallocortices,Plate, Cortical
D003900 Desoxycorticosterone A steroid metabolite that is the 11-deoxy derivative of CORTICOSTERONE and the 21-hydroxy derivative of PROGESTERONE 21-Hydroxyprogesterone,Cortexone,Deoxycorticosterone,Desoxycortone,11-Decorticosterone,21-Hydroxy-4-pregnene-3,20-dione,11 Decorticosterone,21 Hydroxy 4 pregnene 3,20 dione,21 Hydroxyprogesterone
D004305 Dose-Response Relationship, Drug The relationship between the dose of an administered drug and the response of the organism to the drug. Dose Response Relationship, Drug,Dose-Response Relationships, Drug,Drug Dose-Response Relationship,Drug Dose-Response Relationships,Relationship, Drug Dose-Response,Relationships, Drug Dose-Response
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013256 Steroids A group of polycyclic compounds closely related biochemically to TERPENES. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. (From Hawley's Condensed Chemical Dictionary, 11th ed) Steroid,Catatoxic Steroids,Steroids, Catatoxic
D014151 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. Anti-Anxiety Agent,Anti-Anxiety Drug,Anxiolytic,Anxiolytic Agent,Anxiolytic Agents,Tranquilizing Agents, Minor,Anti-Anxiety Drugs,Anti-Anxiety Effect,Anti-Anxiety Effects,Antianxiety Effect,Antianxiety Effects,Anxiolytic Effect,Anxiolytic Effects,Anxiolytics,Tranquillizing Agents, Minor,Agent, Anti-Anxiety,Agent, Anxiolytic,Agents, Anti-Anxiety,Agents, Anxiolytic,Agents, Minor Tranquilizing,Agents, Minor Tranquillizing,Anti Anxiety Agent,Anti Anxiety Agents,Anti Anxiety Drug,Anti Anxiety Drugs,Anti Anxiety Effect,Anti Anxiety Effects,Drug, Anti-Anxiety,Drugs, Anti-Anxiety,Effect, Anti-Anxiety,Effect, Antianxiety,Effect, Anxiolytic,Effects, Anti-Anxiety,Effects, Antianxiety,Effects, Anxiolytic,Minor Tranquilizing Agents,Minor Tranquillizing Agents
D017207 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. Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats
D051379 Mice The common name for the genus Mus. Mice, House,Mus,Mus musculus,Mice, Laboratory,Mouse,Mouse, House,Mouse, Laboratory,Mouse, Swiss,Mus domesticus,Mus musculus domesticus,Swiss Mice,House Mice,House Mouse,Laboratory Mice,Laboratory Mouse,Mice, Swiss,Swiss Mouse,domesticus, Mus musculus

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