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Nicotinic and muscarinic responses of embryonic chick ventricular myocardium to acetylcholine: chronotropic and electrophysiological effects
Author(s) -
SUIGNARDKHASKIYE Gisèle,
RENAUD Didier,
DOUARIN Georges
Publication year - 1988
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(88)90096-2
Subject(s) - chronotropic , acetylcholine , medicine , diastolic depolarization , nicotinic agonist , muscarinic acetylcholine receptor , endocrinology , biology , depolarization , membrane potential , electrophysiology , receptor , biophysics , heart rate , sinoatrial node , blood pressure
Sensitivity of 7‐day‐old chick embryo ventricular heart fragments to acetylcholine was investigated. Low doses mainly produced a positive chronotropic effect, whereas high doses of acetylcholine provoked a decrease in the heart beat rhythm. The positive chronotropic effect of acetylcholine was related to the presence of nicotinic receptors that were evidenced within ventricular myocardium by autoradiography. Membrane potential recording showed that acetylcholine hyperpolarizes the diastolic membrane potential when the drug had a negative chronotropic effect. This effect of acetylcholine on the membrane potential was not observed when the drug had a positive chronotropic effect. In many cases, the diastolic membrane potential exhibited spontaneous small depolarizing potentials. Their amplitude was low and their frequency was irregular. These potentials were suppressed by treatment with α‐bungarotoxin, suggesting that they are triggered by nicotinic receptor activation.