Calcitonin gene-related peptide is a potent vasodilator of bovine retinal arteries in vitro.
Calcitonin gene-related peptide (CGRP) invariably induced a slow acting but potent relaxation of bovine retinal small arteries contracted with PGF2 alpha. Maximal relaxation obtained was 93% and 96% with a pD2-value of 8.97 and 8.86 for rat and human CGRP, respectively; thus the bovine retinal arteries cannot discriminate between CGRP from these two species. The CGRP-induced relaxation was reversible. Substance P was without effect on retinal arteries contracted with PGF2 alpha. Bradykinin relaxed 4 of 18 vessels tested in the concentration range of 11(-11)-10(-8) M whereas the vessels were contracted again at 3 x 10(-8) M. Bradykinin was without effect in the remaining 14 vessels. None of the peptides had a contractile effect on retinal arteries kept relaxed in normal buffer solution. Capsaicin 3 x 10(-5) M induced a relaxation comparable to that obtained by 10(-9) M of CGRP. The capsaicin-induced relaxation was reproducible and it was concentration dependently inhibited by ruthenium red which suggests that capsaicin releases CGRP in the arterial wall. The results indicate that CGRP has a powerful relaxing effect on the retinal vasculature indicating a role for CGRP in ocular blood flow regulation.
Prieto
D
D
Department of Pharmacology, University of Aarhus, Denmark.
Benedito
S
S
Nielsen
P J
PJ
Nyborg
N C
NC
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D012171:Retinal Vessels / Q000187:drug effects*; D012430:Ruthenium Red / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D014665:Vasodilator Agents; D012430:Ruthenium Red; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin; D001920:Bradykinin