Intracellular potential characteristics of some orthopteroid insect hearts

Abstract

1. 1. The heart of the stick insect, Carausius morosus, beats rhythmically for long periods in saline solutions of either high Na or high Mg ion. 2. 2. A plateau phase of the spontaneous electrical potentials in Carausius heart was always evident when bathed in high Mg. The plateau in Carausius intracellular potentials was eliminated by perfusing with a high Na saline. A plateau phase was not ordinarily present in the intracellular potentials from the cockroach heart, Periplaneta americana, when bathed in normally high Na saline. However, a plateau was induced into the electrical potentials by treatment with Sr or Mg ions. 3. 3. The membrane potential of the cockroach heart, P. americana, was directly related to the concentration of potassium ion in the external medium. High potassium concentrations reversibly depolarized the myocardium in K-contracture. 4. 4. Intracellular potential activity in the hearts of Periplaneta, Carausius and the locust, Schistocerca gregaria was characteristic of myogenic pacemakers with a clear generator potential phase.