TY - JOUR T1 - Ethanol-Like Discriminative Stimulus Effects of Endogenous Neuroactive Steroids: Effect of Ethanol Training Dose and Dosing Procedure JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 405 LP - 411 VL - 289 IS - 1 AU - Carrie A. Bowen AU - Robert H. Purdy AU - Kathleen A. Grant Y1 - 1999/04/01 UR - http://jpet.aspetjournals.org/content/289/1/405.abstract N2 - A number of endogenous steroids exhibit rapid, nongenomic effects on the central nervous system and are called neuroactive steroids. The rapid mechanisms of action include modulation of γ-aminobutyric acid type A (GABAA) andN-methyl-d-aspartate (NMDA) receptors, which are two receptors implicated in the behavioral effects of ethanol. It was hypothesized that neuroactive steroids that positively modulate GABAA receptors or negatively modulate NMDA receptors, analogous to the actions of ethanol, would produce discriminative stimulus effects similar to ethanol. Two groups of male Long-Evans rats (n = 6–8/group) were trained to discriminate between 1.0 or 2.0 g/kg ethanol (i.g.) and water (i.g.). The neuroactive steroids allopregnanolone, pregnanolone, epipregnanolone, allotetrahydrodeoxycorticosterone, pregnanolone sulfate, epipregnanolone sulfate, dehydroepiandrosterone, dehydroepiandrosterone sulfate, pregnenolone, and pregnenolone sulfate (PS), all administered i.p., were tested for substitution with acute and cumulative dosing procedures (n = 4–8/steroid). The GABAA-positive modulatory steroids allopregnanolone, pregnanolone, and allotetrahydrodeoxycorticosterone substituted for ethanol, as did the low-efficacy steroid 3β,5β-P. GABAA-negative modulators, such as dehydroepiandrosterone sulfate and PS, and all of the NMDA modulators tested, including PS, pregnanolone sulfate, and epipregnanolone sulfate, did not substitute for ethanol. These results show that certain endogenously occurring neuroactive steroids produce discriminative stimulus effects similar to those of ethanol. The American Society for Pharmacology and Experimental Therapeutics ER -