Association between pituitary adenylate cyclase-activating polypeptide and thyrotropin-releasing hormone in the rat hypothalamus

Pituitary adenylate cyclase-activating polypeptide (PACAP) is present in many regions of the hypothalamus including the paraventricular nucleus (PVN). In this study the anatomical relationship between PACAP- and thyrotropin-releasing hormone (TRH)-immunoreactive neuronal elements was investigated in...

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Bibliographic Details
Published in:Journal of chemical neuroanatomy 1997-10, Vol.13 (4), p.265-279
Main Authors: Légrádi, Gábor, Hannibal, Jens, Lechan, Ronald M
Format: Article
Language:English
Subjects:
Animals
Colocalization
Electron microscopy
Fluorescent Antibody Technique, Indirect
Hypothalamic-pituitary regulation
Immunoenzyme Techniques
Immunohistochemistry
Male
Mice
Microscopy, Electron
Nerve Fibers - chemistry
Neurons - chemistry
Neuropeptides - analysis
Neurotransmitter Agents - analysis
PACAP
Paraventricular Hypothalamic Nucleus - chemistry
Paraventricular Hypothalamic Nucleus - ultrastructure
Paraventricular nucleus
Pituitary Adenylate Cyclase-Activating Polypeptide
Rabbits
Rats
Rats, Sprague-Dawley
Thyrotropin-Releasing Hormone - analysis
TRH
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Summary:Pituitary adenylate cyclase-activating polypeptide (PACAP) is present in many regions of the hypothalamus including the paraventricular nucleus (PVN). In this study the anatomical relationship between PACAP- and thyrotropin-releasing hormone (TRH)-immunoreactive neuronal elements was investigated in the rat hypothalamus. Using a well-characterized mouse monoclonal antibody against PACAP and a rabbit polyclonal antiserum against TRH, we found numerous nerve fibers with PACAP-immunoreactivity (ir) closely apposed to TRH neurons in the PVN suggesting synaptic contacts. Electron microscopy confirmed the presence of synapses between PACAP-ir terminals and TRH-ir perikarya and various dendritic profiles as well as between PACAP-ir terminals and unlabeled perikarya and small- to medium-sized dendrites. Coexistence of the two peptides in perikarya of the PVN was limited to only a few neurons in the periventricular subdivision, but PACAP-ir and TRH-ir extensively coexisted in perikarya of the perifornical cell group, medial preoptic area, lateral hypothalamus and dorsomedial nucleus. The interactions between PACAP-containing neuronal processes and TRH neurons in the PVN raise the possibility that PACAP modulates the secretion of TRH destined for regulation of anterior pituitary TSH. The more general association between PACAP and TRH in other regions of the hypothalamus suggests a further role for PACAP as a cofactor in the function of TRH neurons.
ISSN:0891-0618
1873-6300
DOI:10.1016/S0891-0618(97)10002-3