Pharmacological evidence of an interaction between serotonergic and dopaminergic neurons in the control of prolactin secretion in male rats.

The purpose of the present study was to investigate the possible interaction between serotonergic and dopaminergic neurons in regulating prolactin (PRL) secretion. We have examined the effect of quipazine, a drug which has been reported to increase plasma PRL levels by acting through a serotonergic mechanism, on PRL release in rats pretreated with penfluridol or alpha-methyl-p-tyrosine (alpha-MPT). The effect of d-fenfluramine, a serotonin releaser, on plasma PRL levels in animals pretreated with penfluridol was also studied. Penfluridol or alpha-MPT treatments significantly stimulated PRL secretion. Quipazine also increased plasma PRL levels in normal male rats. However, this drug was not able to further stimulate PRL release in animals pretreated with penfluridol or alpha-MPT. Like quipazine, d-fenfluramine increased plasma PRL levels in normal rats but it failed to further stimulate PRL secretion in penfluridol-pretreated animals. These findings support the hypothesis that serotonin may stimulate PRL release through an inhibition of dopaminergic neurons.