REGULATION OF TYROSINE-HYDROXYLASE GENE-EXPRESSION IN MESENCEPHALIC DOPAMINE NEURONS - EFFECT OF IMIPRAMINE TREATMENT

The effects of a chronic imipramine treatment on the mesoamygdaloid pa thway of rats were examined. Using semiquantitative immunocytochemical techniques, it was observed that the level of TH mRNA was decreased i n the ventral tegmental area (VTA). In contrast, the TH protein was in creased in both the VTA and amygdala. The TH activity was decreased in the amygdala when assessed under normal conditions but increased afte r a preincubation to phosphorylate the enzyme, suggesting a lowering o f the protein-specific activity in the terminals. These results show t hat TH protein turnover in the mesoamygdaloid neurons can be reduced b y chronic imipramine treatments, thereby producing an accumulation of inactive TH protein in the neurons while also decreasing TH gene activ ity in the cell bodies.