Gap Junctions in Vascular Tissues

Integration and coordination of responses among vascular wall cells are critical to the local modulation of vasomotor tone and to the maintenance of circulatory homeostasis. This article reviews the vast literature concerning the principles that govern the initiation and propagation of vasoactive stimuli among vascular smooth muscle cells, which are nominally the final effectors of vasomotor tone. In light of the abundance of new information concerning the distribution and function of gap junctions between vascular wall cells throughout the vascular tree, particular attention is paid to this integral aspect of vascular physiology. Evidence is provided for the important contribution of intercellular communication to vascular function at all levels of the circulation, from the largest elastic artery to the terminal arterioles. The thesis of this review is that the presence of gap junctions, in concert with the autonomic nervous system, pacemaker cells, myogenic mechanisms, and/or electrotonic current spread (both hyperpolarizing and depolarizing waves through gap junctions), confers a plasticity, adaptability, and flexibility to vasculature that may well account for the observed diversity in regulation and function of vascular tissues throughout the vascular tree. It is hoped that the summary information provided here will serve as a launching pad for a new discourse on the mechanistic basis of the integrative regulation and function of vasculature, which painstakingly accounts for the undoubtedly complex and manifold role of gap junctions in vascular physiology/dysfunction.