Dopamine-regulated adrenocorticotropic hormone secretion in lactating rats: Functional plasticity of melanotropes

Márk Oláh, Pálma Fehér, Zsófia Ihm, Ildikó Bácskay, Timea Kiss, Marc E. Freeman, György M. Nagy, Miklós Vecsernyés

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Pro-opiomelanocortin (POMC) is processed to adrenocorticotropic hormone (ACTH) and β-lipotropin in corticotropes of the anterior lobe, and to α-melanocyte-stimulating hormone (α-MSH) and β-endorphin in melanotropes of the intermediate lobe (IL) of the pituitary gland. While ACTH secretion is predominantly under the stimulatory influence of the hypothalamic factors, hormone secretion of the IL is tonically inhibited by neuroendocrine dopamine (NEDA) neurons. Lobe-specific POMC processing is not absolute. For example, D2 type DA receptor (D2R)-deficient mice have elevated plasma ACTH levels, although it is known that corticotropes do not express D2R(s). Moreover, observations that suckling does not influence α-MSH release, while it induces an increase in plasma ACTH is unexplained. The aim of the present study was to investigate the involvement of the NEDA system in the regulation of ACTH secretion and the participation of the IL in ACTH production in lactating rats. Untreated and estradiol (E2)-substituted ovariectomized (OVX) females were also studied. The concentration of ACTH in the IL was higher in lactating rats than in OVX rats, while the opposite change in α-MSH level of the IL was observed. DA levels in the IL and the neural lobe were lower in lactating rats than in OVX rats. Suckling-induced ACTH response was eliminated by pretreatment with the DA receptor agonist, bromocriptine (BRC). Inhibition of DA biosynthesis by α-methyl-p-tyrosine (αMpT) and blockade of D2R by domperidone (DOM) elevated plasma ACTH levels, but did not influence plasma α-MSH levels in lactating rats. The same drugs had opposite effects in OVX and OVX + E2 animals. In lactating mothers, BRC was able to block ACTH responses induced by both αMpT and DOM. Surgical denervation of the IL elevated basal plasma levels of ACTH. Taken together, these data indicate that melanotropes synthesize ACTH during lactation and its release from these cells is regulated by NEDA neurons.

Original languageEnglish
Pages (from-to)391-401
Number of pages11
JournalNeuroendocrinology
Volume90
Issue number4
DOIs
Publication statusPublished - Nov 2009

Keywords

  • Adrenocorticotropic hormone
  • Dopamine
  • Intermediate lobe
  • Lactation
  • α-Melanocyte-stimulating hormone

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

Fingerprint Dive into the research topics of 'Dopamine-regulated adrenocorticotropic hormone secretion in lactating rats: Functional plasticity of melanotropes'. Together they form a unique fingerprint.

  • Cite this