Effects of pinealectomy on regional brain serotonin metabolism

The influence of pinealectomy on serotonin cerebral metabolism was examined in male rats maintained in a long photoperiod (14 h L:10 h D). Eight weeks after pinealectomy, serum, hepatic and CNS concentrations of tryptophan were not affected. The concentrations of 5-HT was significantly decreased in only three regions, hypothalamus, midbrain and hippocampus. The levels of 5-HIAA decreased significantly only in the hypothalamus and the midbrain. These results suggest that pinealectomy promotes a decreased hypothalamic and midbrain 5-HT utilization.