Ag. Alvis et al., Influence of calcitonin gene-related peptide release on pH-induced mechanical depression in rat atria, JPN HEART J, 42(4), 2001, pp. 507-517
Rat atria is richly innervated by sensory nerve fibers that release CGRP wh
en stimulated either by capsaicin or acid pH. We studied the physiological
relevance of acid pH-induced CGRP release on changes in atrial contractilit
y and relaxation produced by lowering the pH. Isolated atria electrically p
aced at 2.77 Hz were exposed to a 10-minute period of metabolic acidosis (p
H = 6.73 +/- 0.01, n=28) after: 1) CGRP release induced by capsaicin 0.5 mu
M, 2) blockage of CGRP release with ruthenium red (RR) 5 muM; 3) no pretrea
tment; and 4) CGRP receptor blockage with CGRP(8-37) 1 muM. Contractility a
nd relaxation were significantly less depressed by acid pH when CGRP releas
e was prevented by RR or CGRP receptor activation was blocked by CGRP(8-37)
. The results suggest that CGRP release and the activation of CGRP receptor
s may be physiologically involved in contributing to the depression of cont
ractility and relaxation induced by acid pH in rat atria.