title: Neurosteroidal modulation of social isolation-induced decrease in pentobarbital sleep in mice.
abstract: Stressful manipulations are known to change the level of neurosteroids capable of interacting with GABAA receptor in the brain. To clarify the involvement of these neurosteroids in social isolation stress-induced decrease in pentobarbital sleep in mice, we examined the effects of 3 beta-hydroxy-5-pregnen-20-one-3-sulfate (pregnenolone sulfate, PS), a steroidal GABAA antagonist, and 3 alpha,21-dihydroxy-5 alpha-pregnan-20-one (allo-THDOC) and 3 alpha,21-dihydroxy-5 beta-pregnan-20-one (THDOC), positive allosteric modulators of the GABAA receptor, on the hypnotic activity of pentobarbital in socially isolated mice. Pentobarbital (50 mg/kg, i.p.)-induced sleep was significantly shorter in isolated mice than in group-housed mice and adrenalectomy had no effect on the decrease of pentobarbital sleep following social isolation. PS (5-10 mg/kg, i.p. or 12-24 nmol, i.c.v.) decreased pentobarbital sleep in group-housed mice in a dose-dependent manner without affecting the sleep in socially isolated mice. In contrast, allo-THDOC (14.9-37.4 nmol, i.c.v.) and THDOC (5-12.5 mg/kg, i.p. or 14.9-37.4 nmol, i.c.v.) reversed the pentobarbital sleep decreased by social isolation to the level in group-housed mice. These steroids had no effect on the pentobarbital sleep in group-housed mice. Such a reversing effect of THDOC in isolated mice was significantly blocked by PS (24 nmol, i.c.v.). Moreover, i.c.v. injection of yohimbine (30 nmol), methoxamine (200 nmol) and CRF (2.1 nmol) significantly decreased pentobarbital sleep in group-housed mice but not that in isolated mice. The effects of these drugs on pentobarbital sleep in group-housed mice were significantly attenuated by THDOC (12.5 mg/kg, i.p.). These results suggest that changes in the level of neurosteroids with ability to modulate GABAA receptor function are involved in social isolation-induced decrease in the hypnotic activity of pentobarbital in mice.
authors.affiliation: Division of Pharmacology, Toyama Medical and Pharmaceutical University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
authors.forename: K
authors.initials: K
authors.lastname: Ojima
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000315:Adrenalectomy; D000494:Allosteric Regulation; D000704:Analysis of Variance; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D010424:Pentobarbital; D011284:Pregnenolone / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology*; D012890:Sleep; D012919:Social Behavior; D012934:Social Isolation; D013315:Stress, Psychological; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D014151:Anti-Anxiety Agents; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; C018370:pregnenolone sulfate; D015016:Yohimbine; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D011284:Pregnenolone; D003346:Corticotropin-Releasing Hormone; D008729:Methoxamine; D010424:Pentobarbital