Circulating beta-endorphin (beta EP) and beta-lipotropin (beta LPH) concentrations increase after the administration of acetylcholine or serotonin agonist drugs. In this study we examined the effect of dopamine receptor agonists and/or antagonists on plasma beta EP, beta LPH, cortisol, and PRL levels in normal subjects. Neither direct dopamine (DA) agonist drugs, DA (1 microgram/kg min for 120 min), bromocriptine (2.5 mg po), L-dopa (500 mg po) or an indirect DA agonist, nomifensine (200 mg po), significantly altered plasma beta EP and beta LPH levels. The administration of metoclopramide, a DA antagonist (10 mg iv), significantly increased plasma beta EP, beta LPH, PRL, and cortisol levels. This effect was completely reversed by pretreatment with L-dopa (500 mg po) and only partially antagonized by DA infusion. Domperidone (10 mg iv), a DA antagonist which does not cross the blood brain barrier, increased only plasma beta EP levels, an effect inhibited both by L-dopa and DA. After dexamethasone (2 mg/day for 2 days) domperidone still increased plasma beta EP and PRL levels. The concomitant increase of beta EP, beta LPH, and cortisol after metoclopramide suggests that endogenous DA inhibits the secretion of proopiomelanocortin-related peptides. Moreover, since domperidone increases only beta EP and this effect is not altered by dexamethasone, there may be a corticotropin-releasing hormone-independent source of circulating beta EP in humans, which is inhibited by DA.

Evidences for a dopamine-regulated peripheral source of circulating beta-endorphin.

GENAZZANI, ANDREA;
1988

Abstract

Circulating beta-endorphin (beta EP) and beta-lipotropin (beta LPH) concentrations increase after the administration of acetylcholine or serotonin agonist drugs. In this study we examined the effect of dopamine receptor agonists and/or antagonists on plasma beta EP, beta LPH, cortisol, and PRL levels in normal subjects. Neither direct dopamine (DA) agonist drugs, DA (1 microgram/kg min for 120 min), bromocriptine (2.5 mg po), L-dopa (500 mg po) or an indirect DA agonist, nomifensine (200 mg po), significantly altered plasma beta EP and beta LPH levels. The administration of metoclopramide, a DA antagonist (10 mg iv), significantly increased plasma beta EP, beta LPH, PRL, and cortisol levels. This effect was completely reversed by pretreatment with L-dopa (500 mg po) and only partially antagonized by DA infusion. Domperidone (10 mg iv), a DA antagonist which does not cross the blood brain barrier, increased only plasma beta EP levels, an effect inhibited both by L-dopa and DA. After dexamethasone (2 mg/day for 2 days) domperidone still increased plasma beta EP and PRL levels. The concomitant increase of beta EP, beta LPH, and cortisol after metoclopramide suggests that endogenous DA inhibits the secretion of proopiomelanocortin-related peptides. Moreover, since domperidone increases only beta EP and this effect is not altered by dexamethasone, there may be a corticotropin-releasing hormone-independent source of circulating beta EP in humans, which is inhibited by DA.
Genazzani, Andrea; Petraglia, F; Facchinetti, F; Golinelli, S; Oltramari, P; Santoro, V; Volpe, A.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/11392
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact