Effects of volatile anesthetics on force interval relationships in guinea-pig atrial preparations

モルモット心房筋の張力頻度関係および張力回復に及ぼす揮発性麻酔薬の効果

Effects of volatile anesthetics on force interval relationships in guinea-pig atrial preparations

Creators Saka Yasuo

Depressant effects of halothane, enflurance and isoflurance on isolated guinea pig right atrial muscles bathed in Tyrode's solution at 30℃ were examined. Contractions were elicited by stimulation through external field electrodes while tension was recorded continuously. Frequency-force relationships at stimulation rates of 0.1, 0.2, 0.5 and 1Hz were studied. The pD_2 values of these volatile anesthetics at each stimulation rates were not different significantly, suggesting the frequency-independent depressions of these anesthetics. Interval-strength relationships at time intervals of 0.3～20 sec during 1Hz-stimulation were also studied. Mechanical restitution curves after converting to logistic function reached a peak at 8～20sec and were fitted well to double exponential functions with time constants of 200～600 msec (k_1) and 2～6sec (k_2). All volatile anesthetics depressed the magnitude constants for fast response in a dose dependent manner. Accordingly, at high concentrations, mechanical restitution curves were fitted to single exponential functions. Halothane and enflurane did not alter time constants k_1, k_2 significantly, while isoflurane increased k_2 significantly. These results suggest that the mechanisms of myocardial depressant effects are different between these anesthetics.

[ISSN]0513-1731

[NCID]AN00243156