The compound SS-68 attenuates electrophysiological effects of m3 cholinoreceptors stimulation in rat left atrial myocardium

In the present study we have investigated influence of SS-68, which has been previously demonstrated to produce potent antiarrhythmic effects in mammalian myocardium, on the electrophysiological effects of selective M3 cholinoreceptors stimulation in rat atrial myocardium. M3 receptors were activated with muscarinic agonist pilocarpine (10 jM) in the presence of highly selective blocker of M2 cholinoreceptors methoctramine (100 nM). In isolated left atrial preparations M3 stimulation produced reduction of action potential duration by 20 ± 2,2% of control duration. SS-68 (10 jM) decreased intensity of action potential shortening more than twice - to 7,9 ± 1,1% of control action potential duration. SS-68 also suppressed action potential shortening produced by pilocarpine in the absence of M2 antagonist. Thus, compound SS-68 attenuates effect of joint activation of M2 and M3 receptors as well as the effect of selective M3 stimulation.