Influence of Calcitonin Gene-related Peptide Release on pH-induced Mechanical Depression in Rat Atria

GOMEZ ALVIS ALICIA; MILESI VERONICA; REBOLLEDO ALEJANDRO; RAINGO JESICA; GRASSI DE GENDE ANGELA

JAPANESE HEART JOURNAL

J-Stage

Año: 2001 vol. 42 p. 507 - 517

0021-4868

Rat atria is richly innervated by sensory nerve fibers that release CGRP when stimulatedeither by capsaicin or acid pH. We studied the physiological relevance of acid pHinducedCGRP release on changes in atrial contractility and relaxation produced by loweringthe pH. Isolated atria electrically paced at 2.77 Hz were exposed to a 10-minuteperiod of metabolic acidosis (pH=6.73±0.01, n=28) after: 1) CGRP release induced bycapsaicin 0.5 µM; 2) blockage of CGRP release with ruthenium red (RR) 5 µM; 3) no pretreatment;and 4) CGRP receptor blockage with CGRP8-37 1 µM. Contractility and relaxationwere significantly less depressed by acid pH when CGRP release was prevented byRR or CGRP receptor activation was blocked by CGRP8-37. The results suggest thatCGRP release and the activation of CGRP receptors may be physiologically involved incontributing to the depression of contractility and relaxation induced by acid pH in ratatria.