The effects of aging on the electrophysiologic responses to verapamil in isolated perfused rat hearts

O Schmidlin, J Garcia and JB Schwartz

Department of Medicine, University of California, San Francisco.

The effects of aging on heart rate and atrioventricular (AV) conduction responses to verapamil (0-100 ng/ml) were studied in Langendorff perfused hearts from 12 mature (4-6 months) and 12 senescent (24 months) male Fischer 344 rats and in hearts from 10 mature and 9 senescent rats after reserpine administration (0.25 mg/kg/day i.p. for 5-7 days). During 30 min of perfusion with verapamil concentrations of 0, 10, 20, 50 and 100 ng/ml in the absence of reserpine administration, intervals between atrial electrograms (A-A intervals), paced AV conduction time and AV Wenckebach cycle lengths increased in hearts from all animals (P less than .001). A-A intervals increased more in senescent vs. mature animals (with marked slowing in 3/12 senescent and 0/12 mature at 100 ng/ml), spontaneous AV Wenckebach block occurred more frequently in hearts from senescent animals (in 7/12 senescent and 1/12 mature, P less than .07) and AV Wenckebach cycle length increased more in senescent vs. mature hearts (from 123 +/- 11 to 294 +/- 108 msec, mean +/- S.D., in mature vs. 154 +/- 16 to 458 +/- 10 msec in senescent hearts). Reserpine administration did not significantly alter qualitative responses to verapamil, but accentuated age differences in responses at higher verapamil concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Volume 258, Issue 1, pp. 130-135, 07/01/1991
Copyright © 1991 by American Society for Pharmacology and Experimental Therapeutics