Connexin-dependent communication within the vascular wall: contribution to the control of arteriolar diameter.

Communication between cells is important to the microcirculation and enables the coordination of cellular behavior along the length of the vessel. Arterioles span considerable distances within the microcirculatory network, and thus flow changes require the adaptation of vessel resistance over the whole length of the vessel in order to be effective. Such a task requires communication along the vessel wall, and gap junction channels that connect endothelial as well as smooth muscle cells with each other set the stage for this requirement. Communication along the vessel wall can be tested experimentally by confined local stimulation of arterioles either in vitro or in vivo. Certain vascular stimuli induce both a local response and a concomitant uniform remote response, confirming the rapid conduction of vasomotor stimuli along the vessel wall. Gap junctions in vascular tissue are composed of connexins (Cx) Cx40, Cx43, Cx37 and Cx45. Of these, Cx40 is of special importance: its lack results in a deficient conduction of vasodilator stimuli along the vessel wall. Interestingly, Cx40-deficient mice display an elevated mean arterial pressure, suggesting that Cx40-depending gap junctional coupling is necessary to regulate vascular behavior and peripheral resistance. While the role of other connexins is less well established, an abundance of experimental data has proven the necessity of gap junctional communication to coordinate vascular behavior during adaptive blood flow regulation.