Central neural influence on precapillary microvessels and sphincter.

The responses to central nervous system (CNS) stimulation of consecutive segments of arterioles down to the precapillary sphincter were measured in the mesoappendix and/or cremaster of nine male rats with indwelling electrodes. Under pentobarbital sodium anesthesia, vasoactive sites were stimulated at threshold for maximal constriction or lumen closure of the precapillary sphincter and/or immediately preceding precapillary arteriole (metarteriole). In all experiments, CNS stimulation induced blood pressure elevation and constriction of three consecutive segments of precapillary vessels and of the sphincter. A threefold increase in rate of vasomotion of precapillary sphincter and metarteriole was the rule, but this was noted infrequently in larger arterioles. In addition to an overall influence of the CNS on microcirculation, the data show a gradient of responses to stimulation, the slope of which is negatively related to the size of the vessels and sphincter, in both tissues studied. A complete lumen clos...