Symposia Biologica Hungarica 17. - Symposium on the Muscle (1976)
Excitation - Varga, E. - Dankó, M. - Domonkos, J. - Gesztelyi, I.: Investigation of metabolic dependency of membrane potential oscillation evoked by veratrine on skeletal muscle
Symp. Biol. Hung. 17, pp. 101 — 104 (1974) INVESTIGATION OF METABOLIC DEPENDENCY OF MEMBRANE POTENTIAL OSCILLATION EVOKED BY VERATRINE ON SKELETAL MUSCLE by E. Vakga, M. Dankó, J. Domonkos and I. Gesztelyi DEPARTMENT OE PHYSIOLOGY, UNIVERSITY MEDICAL SCHOOL, DEBRECEN, DEPARTMENT OE NEUROLOGY AND INSTITUTE OE BRAIN RESEARCH, SZEGED, HUNGARY Two years ago we published our experiments showing that following veratrine treatment the sartorius muscle exhibits expressed rhythmic membrane potential oscillations for hours (Varga et ah, 1972). In our experiments we recorded the veratrine evoked oscillations of membrane potential generally by extracellular conduction from all fibres of the aneural part of the sartorius muscle according to the method of Gesztelyi (Gesztelyi, 1973). The rhythmic membrane potential oscillation caused by veratrine could also be observed, however, by intracellular conduction from one superficial fibre of the sartorius muscle (Varga et ah, 1975). In our earlier experiments we established the temperature dependency of the phenomenon. A critical value of temperature about 13-14 °C was found below which practically no oscillation can be observed and above which the further increase of the temperature does not change it anymore (Varga et ah, 1975). We have observed further that the developed oscillation of membrane potential can be inhibited by 1 mM monoiodic acetic acid, and 10 mM Nafluoride, respectively. The inhibiting effect of Na-fluoride could be reversed by a treatment of fluoride-free Ringer containing Mg (Varga et ah, 1975). In our above experiments we investigated first of all how oscillation of the membrane potential evoked by veratrine is influenced by oxygenation of the incubating Ringer’s solution. In the studies the muscle specimen incubated in oxygen-free medium was used as control, while the incubating solutions of other samples were oxygenated for different time during the experiment (Fig. 1). Upon the effect of oxygenation the frequency of oscillation increased from 0.4 cycle/min to 0.6 cycle/min. The amplitude began to decrease later and oscillation ceased after about a half an hour. Further we investigated the effect of two compounds having characteristic metabolic site of action (Fig. 2). This characteristic record shows the effect of K-cyanide which inhibits terminal oxydation. In these experiments oscillation of the membrane potential was evoked on both members of the muscle pair incubated in oxygenated medium. Later one of them was treated with 1 mM K-cyanide, as a result of which the oscillation entirely ceased in about 15 min (Fig. 3). The effect of 0.1 mM dinitrophenol is shown in an oxygenated medium. In this concentration which uncouples oxidative phosphorylation dinitrophenol inhibits the oscillation of the membrane potential, too. Finally the pH-dependency of the phenomenon was studied by cornpar-