Efeitos do estresse crônico moderado imprevisível sobre o metabolismo da serotonina na matéria cinzenta periaquedutal e sobre os comportamentos dos tipos ansioso e depressivo em ratos adultos

Abstract

It is generally accepted that the inability to control chronic stress facilitates the development of depression. On the other hand, epidemiological data showed that depression is highly comorbid with panic. Moreover, plenty evidence suggests that serotonin (5-HT) is crucial in both panic and depression. Therefore, here we evaluated the effect of unpredictable chronic mild stress (UCMS), a presumptive model of depression, on 5-HT metabolism at the periaqueductal gray matter of the midbrain (PAG), a presumptive substrate of panic. UCMS rats were also evaluated with regard to the baseline levels of depression (forced swimming) and anxiety (elevated plus-maze, open-field), Adult male rats were subjected to a 9-day UCMS. The day after, the rats were decapitated and the brains were removed along with a trunk blood sample. Punches of dorsal and ventrolateral PAG were then assayed for 5-HT and its main metabolite, 5-hydroxyindoleacetic acid (5-HIAA). Corticosterone plasma levels were assayed as well. Data showed no effects of UCMS either in depression or anxiety baseline levels. Compared to non-stressed controls, UCMS rats showed significant increases in 5-HT levels of dorsal PAG only. Although the 5-HIAA levels did not differ among groups, 5-HT turnover was significantly reduced in ventrolateral PAG. UCMS rat weight was significantly reduced relative to controls in spite of the lack of effects in corticosterone plasma levels. Data suggest that UCMS differentially affect 5-HT levels in dorsal and ventrolateral PAG.