Evidence for 5-HT(1A) receptor control of pineal melatonin concentrations in the rat

Abstract

The effect of some serotonin agonists on day and night-time melatonin in the pineal gland was investigated in male rats. Dose dependent increases in nocturnal melatonin concentrations were observed for all serotonin agonists investigated. Statistically significant increases were observed only for D-fenfluramine (20 mg/kg) and the full 5-HT(1A) agonists S(+)-20499 (10 mg/kg, 20 mg/kg) and flesinoxan (20 mg/kg). Both paroxetine and D-fenfluramine dose dependently increased day-time pineal melatonin, but only for D-fenfluramine (20 mg/kg) was there a statistically significant increase. The data suggest that acute increases in synaptic serotonin concentrations can be used to manipulate day- or n..