Electrophysiological studies on the effects of mianserin, a tetracyclic antidepressant agent, on isolated guinea-pig papillary muscle.

We studied the effects of mianserin on the action potentials of papillary muscle from the guinea-pig. Mianserin (above 10 microM) reduced the maximum rate of the rise (Vmax) of the action potential, and shifted the Vmax-Em relationship to more negative potentials. The compound also depressed the slow action potentials of K+-depolarized papillary muscles. It is concluded that relatively high concentrations of mianserin had an inhibitory action on the electrophysiological properties of both the fast- and slow-response fibers of the heart.