Why are Smooth Muscle Responses Unable to Conduct Along Skeletal Muscle Arteries?

Electrical responses initiated in endothelial but not smooth muscle cells conduct robustly along skeletal muscle resistance arteries. The origin of this dichotomy is uncertain and was the focus of this investigation. Computational models based on physical and electrical properties of vascular cells provide two rationalizations for the inability of smooth muscle responses to conduct. First, given the differential orientation of vascular cells and the known variability in coupling resistance, it is conceivable that a resistance artery is inherently designed to limit the conduction of smooth muscle‐initiated responses. This view is consistent with the inability of a high K + solution, discretely applied to stimulate smooth muscle, to elicit a conducted response. Second, given the passive nature of an artery's electrical properties, some smooth muscle agonists may fail to elicit the local electrical response required for conduction. This was confirmed by focally applying phenylephrine and monitoring vasomotor and electrical responses in hamster retractor muscle feed arteries. Further experiments revealed no evidence that the electrical feedback mechanisms in smooth muscle or endothelial cells limit the conduction of smooth muscle responses. In closing, this study highlights that the inability of smooth muscle responses to conduct is due to the inherent biophysical properties of resistance arteries. Supported by the Heart and Stroke Foundation of Canada.