Substance P mechanisms in the regulation of striated muscle microcirculation

Abstract

The effects of substance P (SP) on microvessels in the cremaster of sodium pentobarbital-anesthetized male, Sprague-Dawley rats were investigated using closed-circuit television microscopy. Topically added SP (bath concentrations of 10 −13 to 10 −8 M) caused significant dilation of small arterioles. SP vasodilation was sensitive to pretreatment of the muscle tissue with SP analogues, [ d-Arg 1, d-Pro 2, d-Trp 7,9, Leu 11]-substance P (APTL-SP) and [ d-Pro 2, d-Trp 7,9]-substance P (PT-SP). Attenuation of the responses by pyrilamine suggests that part of the SP-induced dilation involves the release of histamine. The vasodilation was abolished by hydroquinone, suggesting an intermediate role for endothelium-derived relaxing factor in the response to SP.