The resistance of the cardiac muscarinic receptor to chronic ethanol ingestion in the rat.

Abstract

The chronic consumption of alcohol has been correlated with the development of cardiomyopathy and dysrhythmias. These disorders may be secondary to changes in the outflow of the autonomic nervous system. This study looked at the changes in cardiac cell responsiveness to carbamylcholine (CBL) and the concentration of muscarinic receptors. The studies were carried out on hearts excised from male Long-Evans hooded rats, pair-fed on ethanol (E) or control (C) liquid diet. The ethanol diet supplied 35-39% of calories as ethanol. The studies were carried out after 8-10 wks or 18-20 wks on the diet. Ventricular muscarinic receptors were measured using (-)-[3H]quinuclidinyl benzilate (QNB). These studies showed no significant difference in muscarinic receptor concentration or the dissociation constant for [3H]QNB binding after 8-10 wks or 18-20 wks of E ingestion. Electrophysiologic studies of chronotropic responsiveness to CBL showed no significant difference between the E and C groups after 8-10 wks or 18-20 wks. The responsiveness of subsidiary pacemaker cells to CBL was not different between E and C groups at 18-20 wks. These data indicate that chronic E ingestion for up to 20 wks did not effect the cardiac muscarinic receptor concentration or cholinergic response.