Depletion of calcitonin gene-related peptide (CGRP) by capsaicin in cerebral arteries.
Effects of capsaicin in vivo and in vitro on calcitonin gene-related peptide (CGRP)-containing nerves were examined in cerebral arteries. CGRP-like immunoreactive (CGRP-I) nerves were demonstrated in cerebral arteries of rats, guinea pigs and rabbits. The overall distribution of CGRP-I nerves was similar to that of substance P-containing nerves. Since the distribution of CGRP-I nerves of cerebral arteries among these species was the densest in guinea pigs, this animal was used to study the effect of several treatments on CGRP-I nerves. Catecholamine (CA)-fluorescence but not CGRP-I nerves was abolished by surgical sympathectomy or reserpine pretreatment. Pretreatment of the animal with capsaicin abolished CGRP-I nerves of cerebral arteries. CGRP-like immunoreactivity disappeared from cerebral arteries by in vitro incubation with capsaicin. Capsaicin treatment in vivo and in vitro did not affect CA-fluorescence nerves in these arteries. Since capsaicin selectively affects primary afferent nerves, it is suggested that CGRP is contained in sensory nerves. Capsaicin may be a valuable tool in elucidating the physiological or pathophysiological role of CGRP in cerebral circulation.
D000818:Animals; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin / Q000494:pharmacology*; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D006651:Histocytochemistry; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity
D009479:Neuropeptides; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin