Origin of cocaine- and amphetamine-regulated transcript-containing axons innervating hypophysiotropic corticotropin-releasing hormone-synthesizing neurons in the rat

Gábor Wittmann, Zsolt Liposits, Ronald M. Lechan, Csaba Fekete

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33 Citations (Scopus)

Abstract

Cocaine- and amphetamine-regulated transcript (CART) has stimulatory effects on the hypothalamic-pituitary-adrenal axis through direct effects on hypophysiotropic CRH neurons. Recently CART-containing axons have been demonstrated to densely innervate the hypophysiotropic CRH neurons. Based on the sources of the CART-immunoreactive (IR) innervation of the paraventricular nucleus, the putative origins of these CART-containing fibers include neurons of the hypothalamic arcuate nucleus that coexpress αMSH and medullary adrenaline-producing neurons. To determine whether these cell groups contribute to the CART innervation of the hypophysiotropic CRH neurons, we performed a quadruple-labeling immunofluorescent study using antisera against CRH, CART, αMSH, and phenylethanolamine-N-methyl-transferase (PNMT), the latter as a marker for adrenaline. Consistent with previous observations, PNMT- and CART-IR axons densely innervated all CRH neurons, whereas the αMSH-IR innervation was sparse. Although approximately 60% of CART-IR varicosities in juxtaposition to CRH neurons cocontained PNMT, only approximately 18% of them were immunopositive for αMSH. All αMSH-IR boutons and approximately 90% of PNMT-containing varicosities on the surface of CRH neurons were also labeled for CART. The remaining 22% of CART axon varicosities in contact with CRH neurons contained neither αMSH nor PNMT. These results indicate that medullary adrenergic/CART neurons are the major source for the CART innervation of CRH neurons in the paraventricular nucleus; however, to a lesser extent the arcuate nucleus also contributes to the CART-IR innervation of these neurons. The observation that nearly 20% of the CART-IR afferents contain neither αMSH nor PNMT, however, suggests that additional sources also contribute to the CART-IR input of hypophysiotropic CRH neurons.

Original languageEnglish
Pages (from-to)2985-2991
Number of pages7
JournalEndocrinology
Volume146
Issue number7
DOIs
Publication statusPublished - Jul 1 2005

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ASJC Scopus subject areas

  • Endocrinology

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