Effect of stress on activity of the serotoninergic system in limbic brain structures and its correlation with pituitary-adrenal function in the rat.

Fifteen min after ether stress, the 5-hydroxytryptamine (5-HT) content of the rat hypothalamus decreased, while after electric shock no decline was noted in the mesencephalon and the hypothalamus. At 30 min an increase occurred in the mesencephalon and amygdala and at 60 min in the hypothalamus after both stressors. Fifteen min after electric shock the 5-hydroxyindoleacetic acid (5-HIAA) content was increased in the amygdala, while after both stressors in the mesencephalon and hypothalamus 30 min and after ether stress in the amygdala. In the hippocampus and the septum the 5-HT or 5-HIIA content was unaffected by either type of stress. 5-HT turnover decreased between 10 and 20 min after ether stress in the hypothalamus and after electric shock in the mesencephalon and hypothalamus. Between 50 and 60 min after electric shock, 5-HT turnover increased in the mesencephalon. Other brain areas showed no significant difference from the control 5-HT value. 3H-5-HT uptake decreased in the mesencephalon and hypothalamus 20 min after ether stress, but returned to normal after 60 min. The plasma corticosterone level was highest at 30 min after both stressors and returned to normal 90 min after stress. Therefore, the stress-induced decrease of serotoninergic activity in certain limbic brain structures, especially in the hypothalamus, suggests an inverse relationship with pituitary-adrenal activity. This finding would further support the concept that the serotoninergic system plays an inhibitory role in pituitary-adrenal function.