Paraventricular nucleus serotonin mediates neurally stimulated adrenocortical secretion

The purpose of this study was to further elucidate the role of serotonin (5-HT) in adrenocortical regulation. The effects of stimulating the frontal cortex and extrahypothalamic limbic structures, on plasma corticosterone (CS) responses, were studied in rats with vehicle or 5,7-dihydroxytryptamine (5,7-DHT) injection into the midbrain raphe nuclei. In another group of rats the neurotoxin was injected locally into the paraventricular nucleus (PVN) in view of its importance in adrenocortical regulation, and the effects of photic and dorsal hippocampal stimulation on plasma CS were studied. 5,7-DHT caused a significant depletion of hypothalamic 5-HT and blocked the rise in plasma CS following the stimulation of the above neural modalities. These studies suggest that the PVN 5-HT mediates the adrenocortical responses following afferent neural stimuli.