title: Aquaporin-4 water channels in enteric neurons.
abstract: Aquaporin-4 is a water channel predominantly found in astrocytes in the central nervous system and is believed to play a critical role in the formation and maintenance of the blood-brain barrier and in water secretion from the brain. As enteric glial cells were found to share several similarities with astrocytes, we hypothesized that enteric glia might also contain aquaporin-4. We used immunohistochemistry to identify aquaporin-4 in the myenteric and submucosal plexuses of the mouse and the rat colon. We found that subpopulations of neurons in both enteric plexuses were positively labeled for human aquaporin-4. Double staining of the enteric ganglia with antibodies to the neuronal marker neurofilament-heavy chain 100 and to aquaporin-4 showed that a minority of myenteric neurons were aquaporin-4 positive (about 12% in the mouse and 13% in the rat). In contrast, in the submucosal plexus significant numbers of neurons were positive for aquaporin-4 (about 79% in both the mouse and the rat). Double labeling for aquaporin-4 and for the glial marker glial fibrillary acidic protein verified that glial cells were not immunoreactive to aquaporin-4. We further confirmed our findings with additional aquaporin-4 antibodies and Western blot analysis. We found that, in addition to expressing aquaporin-4, the myenteric plexus and, to a greater extent, the submucosal plexus both expressed aquaporin-1. We conclude that neurons rather than glial cells contain aquaporin-4 in the colonic enteric plexuses. It is known that submucosal neurons control transport processes in the intestinal mucosa, and the high percentage of aquaporin-4-positive submucosal neurons suggests that aquaporin-4 contributes to this function.
authors: Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, USA.
authors: Mia M
authors: MM
authors: Thi
authors: David C
authors: DC
authors: Spray
authors: Menachem
authors: M
authors: Hanani
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D015153:Blotting, Western; D003106:Colon / Q000294:innervation* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009197:Myenteric Plexus / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D013368:Submucous Plexus / Q000378:metabolism*
chemical_list: C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein