Effect of the neurotoxin apamin on ion currents in membranes of heart fibers

: It has been shown on auricle fibres of the frog that neurotoxin apamin in extremely low concentrations (10(-10)-10(-9) M) suppresses the current entering in the cell through calcium channels of the membrane, but it increases tonic contraction related to Na/Ca exchange. No significant effects on fast sodium and potassium channels were observed. The results show that the mechanism of apamin effect on the heart is to a large extent conditioned by specific influence on Ca transport through the cell membranes.