Increased sensitivity to 5-hydroxytryptamine due to intraventricular administration of 5,6-dihydroxytryptamine.

The possibility that intraventricular administration of 5,6-dihydroxytryptamine (5,6-DHT) can cause a development of denervation hypersensitivity to central 5-hydroxytryptamine (5-HT) was examined in rats with special reference to the pituitary-adrenocortical functions. Pretreatment with intraventricular injection of 5,6-DHT itself did not affect the basal concentrations or stress-induced increases of plasma B. The same pre-treatment, however, elicited augmented responses to subcutaneous injection of 5-HTP, i.e. there was a significant rise in the concentrations of plasma B as compared with those in the controls. These results suggest a development of denervation hypersensitivity to 5-HT following intraventricular injection of 5,6-DHT.