Diazepam, but not buspirone, induces similar anxiolytic-like actions in lactating and ovariectomized Wistar rats

Previous reports indicate that the behavioural effects (including anxiolytic-like actions, hypothermia, "serotonergic syndrome," maternal behaviour and aggression and reduction in ambulation) of the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), are completely blocked in lactating rats. The present study compares the behavioural effects of buspirone (1.25, 2.5 and 5.0 mg/kg) and diazepam (0.5, 1.0, 2.0 and 4.0 mg/kg) between ovariectomized and mid-lactating rats. The study was carried out on Wistar female rats under inverted light/dark cycle conditions, by using the burying behaviour paradigm, the elevated plus maze and a general activity test. In both ovariectomized and lactating rats, diazepam produced a dose-dependent reduction in burying behaviour and an increase in the time spent in open arms, responses interpreted as anxiolytic. Buspirone at all doses (1.25, 2.5 and 5.0 mg/kg) produced clear motor impairments in lactating, but not in ovariectomized animals, indicating that the effects of this drug on the anxiety paradigms are unspecific. Diazepam, by contrast, at the highest dose (4.0 mg/kg) similarly inhibited ambulation in both conditions. In the elevated plus maze, control lactating subjects spent more time in the open arms compared with saline-treated ovariectomized subjects, suggesting an anxiolytic-like effect of lactation per se. The present results support the idea that some behavioural actions of drugs acting at the serotonergic system vary between ovariectomized and lactating rats. (C) 2001 Elsevier Science Inc. All rights reserved.