Electrical and mechanical activity of frog's heart in electrolyte-free solutions

Abstract

Frog's heart continues to beat in half isotonic solution of sucrose, 0.112 m, for 2-3 hr. The mechanical activity in sucrose is accompanied by electrical activity. After the heart has adjusted to sucrose, sodium chloride produces a temporary inhibition before rhythmic beats are restored. The effect of epinephrine and norepinephrine is reversed; they produce inhibition instead of stimulation after the heart has become adapted to the sucrose solution. Acetylcholine produces inhibition. As an explanation of excitatory phenomena in electrolyte-free solutions, it is suggested that responses are due to activation of intracellular excitation and conduction mechanisms, and that the external ions only condition the membrane.