[A pharmaco-ethological study of the GABA-ergic mechanisms regulating the depression-like behavior of mice]

It is known that repeated stress may result in depression-like alterations of behavior. This behavior is characterized by decreased social exploratory activity and increase in occurrence of defensive postures in a social interaction test in mice. The passive defensive behavior is effectively antagonized by antidepressant drugs thus providing a useful animal model of depression. Effects of several GABAergic drugs were studied in opponent test in individually housed male mice. For two weeks preceding the test, mice were repeatedly exposed to foot shock stimulation and/or social confrontation with an aggressive mouse. Muscimol, a selective agonist of GABA(A) receptors, decreased the frequency and duration of defensive postures and increased the duration of some forms of individual activity (grooming and eating), like the agonist of GABA(B) receptors baclofen. Muscimol was the only compound that facilitated exploratory activity towards an unfamiliar partner and did not suppress the locomotion. Effects of another agonist of GABA(B) receptors phenibut and inhibitor of GABA transaminase valproate Na were less specific and consisted in general suppression of behavior (prevalence of static forms of behavior). It can be thought that GABA(A) receptors are essential for regulation of depression-like behavior of mice.