Inhibition of prolactin release by stimulation of presynaptic serotonin autoreceptors

The effects of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), a serotonin agonist with a preferential action on presynaptic autoreceptors, on prolactin release in male rats was determined. Basal serum prolactin levels were not altered after administration of 1.0, 2.0, 5.0, 10.0 or 20.0 mg/kg of 5-MeODMT. Pretreatment with 5-MeODMT reduced prolactin release by agents that depend on serotonergic neurotransmission for part of their prolactin release stimulation. Prolactin release in response to L-5-hydroxytryptophan (5-HTP) or morphine was significantly reduced by pretreatment of the rats with 5-MeODMT. The results of this experiment indicate that 5-MeODMT acts as a presynaptic serotonin autoreceptor stimulant and not as a post-synaptic serotonin agonist on the neuronal systems that control prolactin release.