Connexin Expression in pial and penetrating cerebral arterioles of the rat

Abstract

Intracerebral, penetrating arterioles provide a conduit by which parenchymal dilator signals are relayed to upstream cerebral arteries. Vascular conduction likely is regulated by the expression of gap junctions, which provide the most direct pathway for intercellular coupling. However, little is known regarding gap junctional connexin expression in penetrating arterioles. In this study, we compared the expression of connexin (Cx) 37, 40, 43 and 45 in penetrating arterioles with that in pial arterioles. Arterioles were isolated from the cortices of Sprague Dawley rats; connexin expression was determined by immunofluorescence staining and confocal laser microscopy. In both types of vessels, Cx37 immunostaining was observed mainly in smooth muscle, whereas Cx40 was found in both smooth muscle and endothelium. Cx43 staining appeared to be restricted adventitially to leptomeningeal tissue, but was absent in vascular cells. In penetrating arterioles, Cx43 punctate labeling was associated with aquaporin‐4 positive processes that envelop the vessels, suggesting the presence of astrocytic end‐feet. Aquaporin‐4 staining was also found in leptomeningeal tissue associated with pial arterioles. There was no evidence of Cx45 expression in these vessels. We conclude that both pial and penetrating cerebral arterioles have a similar distribution of vascular connexin expression. Funded by AHA 0755770Z.