[Inotropic effect of chlorpromazine on the frog atrium].

The chlorpromazine, a calmodulin inhibitor, has been studied for its action on the contraction force and calcium current of the frog atrium fibres. Chlorpromazine (10(-5) mol/l) was observed to induce maximal increase of the contraction force that 30 min after the agent action amounted to (47.3 + 9.3)% of control. The high concentration of chlorpromazine (10(-4) mol/l) produced irreversible decrease in the contraction force. Chlorpromazine (10(-5) mol/l) increased the calcium current by (27.5 +/- 4.8)%. It is supposed that chlorpromazine increases contraction force and calcium current through the inhibition of calmodulin-dependent phosphodiesterase activity.