Forced Swim Test-Induced Endocrine and Immune Changes in the Rat: Effect of Subacute Desipramine Treatment

Abstract

Previously it has been reported that forced swim test (FST) exposure activates the HPA–axis and produces alterations in both cellular and noncellular immunity in rats. Furthermore, there is evidence to suggest that pretreatment with antidepressants has a protective effect against FST-induced immune changes. The purpose of the present study was to examine the effect of subacute treatment with the tricyclic antidepressant desipramine (DMI, 5 and 10 mg/kg; IP) on immobility in the FST, and on FST-induced changes in endocrine and immune parameters in the rat. DMI treatment at a dose of 10 mg/kg produced a significant reduction in immobility time in the FST, while the 5 mg/kg dose was ineffective. FST exposure produced a significant increase in serum corticosterone and a decrease in adrenal ascorbic acid concentrations, neither of which were significantly attenuated by DMI pretreatment. There was a slight but nonsignificant suppression of PHA-induced lymphocyte proliferation 15 min post-FST exposure. However, DMI treatment produced a significant increase in lymphocyte proliferation at this time point. FST exposure caused a reduction in the percentage of lymphocytes and an increase in the percentage of neutrophils in the peripheral blood; DMI treatment failed to significantly alter these stress-induced changes. There was a profound reduction in relative spleen weight observed in DMI-treated animals 120 min post-FST exposure and this was accompanied by an increase in circulating RBC concentrations. In conclusion, although the FST-induced behavioral changes were normalized by DMI treatment the peripheral aberrations induced by FST exposure (with the exception of lymphocyte proliferation) were not. In addition, DMI pretreatment induced stress-like changes in corticosterone, adrenal ascorbic acid and leucocyte subpopulations in the control animals.