Effect of Some Myotropic Substances on Mollusc Hearts

Abstract

The hearts from a number of estuarine molluscs typical of eastern Australian waters have been examined for their response to acetylcholine, adrenaline, noradrenaline, and serotonin. Under the conditions of these experiments Anadara trapezia showed the highest sensitivity to acetylcholine, being depressed by 0·001 p.g/ml. Adrenaline in concentrations of 0·005 p.g/ml produced a decrease in the amplitude of contractions of Regozara flava heart which also responded to 0·01 p.g/ml noradrenaline. Hearts from other species did not respond to catecholamines. Fragum unedo and Regozara jlava heart showed greatest sensitivity to serotonin 'which increased amplitude of contraction. Pinna menkei heart was unresponsive to myotropic substances under the conditions used. The factors affecting sensitivity of response to myotropic substances are discussed.