Evidence that the medial and dorsal raphe nuclei mediate serotonergically-induced increases in prolactin release from the pituitary.
Electrolytic lesions of the medial (MR) or dorsal (DR) raphe nucleus significantly antagonized serum prolactin elevations produced by 5-hydroxytryptophan (5-HTP) in rats pretreated with fluoxetine or citalopram, (serotonin (5-HT) uptake blockers). Lesioned animals in which total blockade of serum prolactin elevations was observed also had total blockade of 5-HT accumulation in the median eminence. However, the increase in serum prolactin levels produced by 5-HTP plus 5-HT reuptake blockade in lesioned rats was not significantly different from sham-operated rats if as little as 15-20% of control median eminence accumulation was present. Serum prolactin elevations produced by quipazine, a direct acting 5-HT agonist, were not significantly affected by MR lesions. On the basis of these results, we suggest that: (1) serum prolactin elevations following 5-HT reuptake blockade plus 5-HTP are correlated with 5-HT concentration in the median eminence; (2) lesion-induced antagonism of 5-HTP-induced prolactin elevation is critically dependent upon complete blockade of median eminence 5-HT accumulation; and (3) 5-HT neurons arising from cell bodies located in the MR and DR are necessary for endogenous serotonergically mediated effects on prolactin secretion in the rat.
D000818:Animals; D001931:Brain Mapping; D001933:Brain Stem / Q000502:physiology*; D015283:Citalopram; D004298:Dopamine / Q000032:analysis; D005473:Fluoxetine / Q000494:pharmacology; D008297:Male; D008473:Median Eminence / Q000032:analysis / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011437:Propylamines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000032:analysis / Q000494:pharmacology*
D011437:Propylamines; D005473:Fluoxetine; D015283:Citalopram; D012701:Serotonin; D011388:Prolactin; D004298:Dopamine