Pharmacological characterization of serotonin receptors involved in the control of prolactin secretion.

The present study was undertaken to characterize the type of serotonin (5-HT) receptors involved in the control of prolactin (PRL) secretion in male rats. d-Fenfluramine (10 mg/kg i.p.), a potent 5-HT releaser and quipazine, (20 mg/kg i.p.) a 5-HT agonist, caused a marked increase in serum PRL levels. Ritanserin (200 micrograms/kg i.p.), a specific antagonist of 5-HT2 receptors, administered 1 h before the administration of d-fenfluramine or quipazine, completely prevented the PRL-releasing effect of these drugs. Furthermore, the administration of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH DPAT) (1.5, 3 and 6 mg/kg i.p.), a compound considered to be a prototypical 5-HT1A agonist, failed to induce any change in serum PRL levels. The same lack of effect on PRL secretion was observed after the administration of 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridin-4-yl)-1-H-indole (RU 24969) (1, 3 and 10 mg/kg i.p.), a compound which has been shown to possess a higher selectivity for 5-HT1B receptor subtypes than for 5-HT1A subtypes. These results suggest that 5-HT receptors involved in the control of PRL secretion are of the 5-HT2 type.