REM-SLEEP DEPRIVATION POTENTIATES THE EFFECTS OF IMIPRAMINE AND DESIPRAMINE BUT NOT THAT OF CLOMIPRAMINE IN THE FORCED SWIMMING TEST

Effects of REM sleep (REMs) deprivation on the basal swimming activity and the tricyclic antidepressants-induced increase in swimming activity in the forced swimming test were investigated. Immediately after a 48-hr period of REMs deprivation, the basal swimming activity in REMs-deprived mice was significantly higher than those in group-housed and socially isolated animals used as the control groups. The REMs deprivation-induced increase in the swimming activity was not changed by adrenoceptor antagonists and it returned to the control levels 3 hr after the REMs deprivation treatment. Moreover, imipramine and desipramine but not clomipramine further increased the swimming activity enhanced by REMs deprivation at doses that did not affect the activity in the control groups. The enhancing effect of REMs deprivation on the sensitivity to imipramine and desipramine remained unchanged even at 3 hr after the REMs deprivation treatment, and it was blocked by the alpha(2)-adrenoceptor antagonist yohimbine. These results suggest that the REMs deprivation-induced increase in basal swimming activity in the forced swimming test is not mediated by adrenoceptor mechanisms, whereas the enhancing effect of REMs deprivation on the sensitivity to imipramine and desipramine may be mediated by the functional changes in alpha(2)-adrenoceptors in the brain.