Protection by capsaicin against attenuated endothelium-dependent vasorelaxation due to lysophosphatidylcholine

Previous studies have shown that pretreatment with calcitonin gene-related peptide (CGRP), a principal transmitter in sensory nerves, can protect the endothelial cell. We therefore evaluated whether in vivo capsaicin treatment prevents endothelial damage elicited by lysophosphatidylcholine (LPC) in the rat aorta. Acute treatment or repeated pretreatment with capsaicin resulted in stimulation of neurotransmitter release from sensory nerves or depletion of their transmitter content respectively. Vasodilator responses to acetylcholine (ACh) were examined in the aorta of these animals. Acute application of capsaicin (50 mg/kg) increased the plasma concentration of CGRP-like immunoreactivity (CGRP-LI) concomitantly with a reversal of the inhibition by LPC of endothelium-dependent ACh-induced relaxation in the isolated rat aorta. After repeated pretreatment with capsaicin to deplete sensory nerve neurotransmitter content the effects of capsaicin were absent as shown by the plasma CGRP-LI concentration and the vasodilator response to ACh. The results demonstrate that systemic capsaicin treatment, which evokes the release of CGRP from sensory nerves, protects the endothelial cell. The present study also suggests that CGRP may be an endogenous vascular protective substance.