Stimulatory effect of the dopa-decarboxylase inhibitor Ro 4-4602 on prolactin release; inhibition by l-dopa, metergoline, methysergide and 2-Br-alpha-ergocryptine
Pontiroli, A.E.; Castegnaro, E.; Vettaro, M.P.; Viberti, G.C.; Pozza, G.
Acta Endocrinologica 84(1): 36-44
1977
ISSN/ISBN: 0001-5598 PMID: 318788 Document Number: 120875
In order to evaluate the role of serotonin (5-HT) in the effect of L-DOPA on prolactin (PRL) release, normal subjects received L-DOPA alone or L-DOPA + a DOPA-decarboxylase inhibitor (Ro 4-4602) in basal conditions and following the repeated administration of metergoline, a specific anit-5-HT agent. The inhibiting effect of L-DOPA on PRL levels was enhanced by metergoline. L-DOPA + Ro 4-4602 however induced a sharp increase in serum PRL levels. This effect was completely abolished by metergoline, which also significantly reduced fasting PRL levels in all the subjects studied. Ro 4-4602 alone induced a significant increase in serum PRL levels, similar to that commonly observed with chlorpromazine and thyrotrophin releasing hormone. The effect was similar in males and females and was reproducible in experiments performed on different days. The effect of Ro 4-4602 was completely abolished by 2-Br- alpha -ergocriptine and metergoline, and to a lesser degree, was reduced by methysergide. These results suggest that Ro 4-4602 is a reliable stimulus to PRL release and show that any stimulus to PRL secretion may be blocked by both dopaminergic and anti-serotonin agents.