Effects of antidepressant drugs on a quickly-learned conditioned-suppression response in mice

Mice experienced to electric shock, exhibited a marked suppression of motor activity when placed in the same cage 24 hr after administration of shocks. Acute administration of imipramine-HCl (10 mg/kg, i.p.), desipramine-HCl (5 and 10 mg/kg, i.p.) and amitriptyline-HCl (5 and 10 mg/kg, i.p.) caused marked reduction of the conditioned suppression of shocked mice, but reduced the motor activity of the non-shocked mice. Maprotiline, mianserin and dimetacrine did not cause reduction of the conditioned suppression. Nialamide (100 mg/kg, i.p.) and pargyline-HCl (100 and 200 mg/kg, i.p.) caused marked reduction of the conditioned suppression but did not increase the motor activity of the non-shocked mice, and tranylcypromine-HCl (10 and 20 mg/kg, i.p.) did not cause reduction of the conditioned suppression. Diphenhydramine-HCl (10 and 20 mg/kg, i.p.) reduced the conditioned suppression of shocked mice in a dose-related manner. Chronic administration of imipramine-HCl (1 and 5 mg/kg, i.p.) for 14 days significantly reduced the conditioned suppression but did not influence the motility rate of the non-shocked mice. Also, chronic administration of amitriptyline (1 mg/kg, i.p.), desipramine (5 mg/kg, i.p.) and dimetacrine (10 mg/kg, i.p.), for 10 days, significantly reduced the conditioned suppression, but did not influence the motility rate of the non-shocked mice. Chronic administration of maprotiline reduced the conditioned suppression. On the other hand, chronic administration of mianserin (5 mg/kg, i.p.) and diphenhydramine (10 mg/kg, i.p.) did not cause a reduction of the conditioned suppression.