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.