Colocalization of connexin 36 and corticotropin-releasing hormone in the mouse brain.
BACKGROUND
Gap junction proteins, connexins, are expressed in most endocrine and exocrine glands in the body and are at least in some glands crucial for the hormonal secretion. To what extent connexins are expressed in neurons releasing hormones or neuropeptides from or within the central nervous system is, however, unknown. Previous studies provide indirect evidence for gap junction coupling between subsets of neuropeptide-containing neurons in the paraventricular nucleus (PVN) of the hypothalamus. Here we employ double labeling and retrograde tracing methods to investigate to what extent neuroendocrine and neuropeptide-containing neurons of the hypothalamus and brainstem express the neuronal gap junction protein connexin 36.


RESULTS
Western blot analysis showed that connexin 36 is expressed in the PVN. In bacterial artificial chromosome transgenic mice, which specifically express the reporter gene Enhanced Green Fluorescent Protein (EGFP) under the control of the connexin 36 gene promoter, EGFP expression was detected in magnocellular (neuroendocrine) and in parvocellular neurons of the PVN. Although no EGFP/connexin36 expression was seen in neurons containing oxytocin or vasopressin, EGFP/connexin36 was found in subsets of PVN neurons containing corticotropin-releasing hormone (CRH), and in somatostatin neurons located along the third ventricle. Moreover, CRH neurons in brainstem areas, including the lateral parabrachial nucleus, also expressed EGFP/connexin 36.


CONCLUSIONS
Our data indicate that connexin 36 is expressed in subsets of neuroendocrine and CRH neurons in specific nuclei of the hypothalamus and brainstem.
Westberg
Lars
L
Laboratory of Neurobiology and Behavior, The Rockefeller University, New York, NY 10021, USA. lars.westberg@pharm.gu.se
Sawa
Evelyn
E
Wang
Alice Y
AY
Gunaydin
Lisa A
LA
Ribeiro
Ana C
AC
Pfaff
Donald W
DW
D000818:Animals; D001933:Brain Stem / Q000166:cytology / Q000378:metabolism*; D022202:Chromosomes, Artificial, Bacterial / Q000378:metabolism; D017630:Connexins / Q000378:metabolism*; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism*; D014018:Tissue Distribution; D000097004:Gap Junction delta-2 Protein
D017630:Connexins; D003346:Corticotropin-Releasing Hormone; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D000097004:Gap Junction delta-2 Protein; C485184:enhanced green fluorescent protein