Distribution of corticotropin releasing hormone receptor immunoreactivity in the rat hypothalamus: Coexpression in neuropeptide Y and dopamine neurons in the arcuate nucleus

Rebecca E. Campbell, Kevin L. Grove, M. Susan Smith

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

An abundance of physiological data suggests an interaction between neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH) in the regulation of endocrine and autonomic functions. Previously, studies in our laboratory have indicated that NPY neurons in the arcuate nucleus of the hypothalamus (ARH) project to and come in close contact with CRH neurons in the paraventricular nucleus of the hypothalamus (PVH). Conversely, it has been demonstrated that the ventromedial portion of the ARH, an area containing NPY neurons, displays CRH receptor binding and CRH receptor mRNA. These data suggest a possible reciprocal feedback regulation between NPY and CRH neurons. The ARH also contains several other populations of neurons that may be targets of the CRH system and express CRH receptors; most notable are tuberoinfundibular dopaminergic neurons (TIDA). The PVH is an important component in the regulation of prolactin secretion and may play a role in the suppression of TIDA activity, which is a critical step in the prolactin stress response. The purpose of the present study was to characterize the distribution and cellular localization of CRH R1 receptor-like immunoreactivity (CRH R1-ir) in the rat hypothalamus and to determine the phenotype of neurons in the ARH that contain CRH R1-ir. CRH R1-ir was present throughout the rat brain. Hypothalamic regions with the highest levels of immunostaining were the supraoptic nucleus, magnocellular PVH, ARH, and suprachiasmatic nucleus. Double label immunofluorescence was used to demonstrate that CRH R1-ir in the ARH was localized to NPY cell bodies. Furthermore, TIDA neurons in the ARH also displayed CRH R1-ir. However, despite an abundance of CRH R1-ir cells in the ARH, CRH-ir fiber innervation to the ARH was extremely sparse. Therefore, although this study provides neuroanatomical evidence for direct CRH R1 regulation of ARH NPY and TIDA neurons in the rat, it is not consistent with the idea of a reciprocal feedback loop and suggests the involvement of other CRH-like ligands, such as urocortin.

Original languageEnglish (US)
Pages (from-to)223-232
Number of pages10
JournalBrain research
Volume973
Issue number2
DOIs
StatePublished - May 30 2003
Externally publishedYes

Keywords

  • HPA axis
  • Hypothalamus
  • Immunofluorescence
  • In situ hybridization
  • Rodent
  • Urocortin

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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