PT - JOURNAL ARTICLE AU - Shannon, Erin E. AU - Porcu, Patrizia AU - Purdy, Robert H. AU - Grant, Kathleen A. TI - Characterization of the Discriminative Stimulus Effects of the Neuroactive Steroid Pregnanolone in DBA/2J and C57BL/6J Inbred Mice AID - 10.1124/jpet.104.082644 DP - 2005 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 675--685 VI - 314 IP - 2 4099 - http://jpet.aspetjournals.org/content/314/2/675.short 4100 - http://jpet.aspetjournals.org/content/314/2/675.full SO - J Pharmacol Exp Ther2005 Aug 01; 314 AB - Neurosteroids represent a class of endogenous compounds that exert rapid, nongenomic effects through neurotransmitter receptor systems such as GABAA. Two neurosteroids, allopregnanolone (3α-hydroxy-5α-pregnan-20-one) and pregnanolone (3α-hydroxy-5β-pregnan-20-one), possess anxiolytic and sedative properties and show substitution for ethanol, benzodiazepines, and barbiturates in drug discrimination assays. This study aimed to examine the effects of strain and sex on the discriminative stimulus effects of pregnanolone. Twelve male and female DBA/2J mice and 12 male and female C57BL/6J mice were trained to discriminate 10 mg/kg pregnanolone from saline. The male C57BL/6J mice had to be removed from the study due to increased seizures apparently associated with the chronic intermittent pregnanolone administration used in drug discrimination. GABAA-positive modulators, neuroactive steroids, N-methyl-d-aspartate (NMDA) antagonists, and 5-hydroxytryptamine (5-HT)3 agonists were tested for pregnanolone substitution. In DBA/2J and C57BL/6J mice, a benzodiazepine, barbiturate, and GABAergic neuroactive steroids all substituted for the stimulus effects of pregnanolone. NMDA antagonists, 5-HT3 agonists, and zolpidem failed to substitute for pregnanolone's discriminative stimulus in either sex or strain. Pentobarbital and midazolam were more potent in producing pregnanolone-like discriminative stimulus effects in DBA/2J mice. Differences in sensitivities to neurosteroids between the two strains were not evident. These results provide a comprehensive look at pregnanolone's discriminative stimulus effects in two commonly used strains of mice. The present data suggest that many of the previously documented neurosteroid-induced behavioral differences between the DBA/2J and C57BL/6J are acute effects and are not apparent in a drug discrimination procedure. The American Society for Pharmacology and Experimental Therapeutics