The effect of infrared laser stimulation of excitable tissue was explained by the rise of temperature that increases the cell membrane capacitance, which causes cell depolarization and action potential activation (Shapiro et al., Nat. Commun. 3:736, 2012). As in cardiac myocytes the relation of cell capacitance and temperature is not well known, we studied the dependence of membrane capacitance on the bath temperature under steady-state conditions in isolated rat ventricular and atrial myocytes. Individual myocytes were whole-cell patch clamped and the membrane capacitance was recorded by the high-resolution square wave stimulation method (Novák and Zahradník, Ann. Biomed. Eng. 34:1201, 2006). The bath temperature was increased by means of a temperature controller at a rate of 0.1°C/s from about 23°C to about 33°C. Experiments on 6 atrial and 3 ventricular myocytes provided an average increase of the cell capacitance by 0.30 ± 0.02 %/°C that corresponds to 0.17 ± 0.03 pF/°C for an average myocyte of 56.6 ± 9.9 pF capacitance (mean ± SEM). The increase of capacitance was proportional to the cell capacitance (R=0.81). There were no significant differences between atrial and ventricular myocytes in the temperature sensitivity of membrane capacitance. The temperature increase caused no mechanical activity or changes in the shape of myocytes. These data are in quantitative agreement with the data obtained on HEK cells and bilayers (Shapiro et al., Nat. Commun. 3:736, 2012) and confirm the effect of temperature on cell capacitance in the case of cardiac myocytes, thus provide an independent support for the theory of optical stimulation of excitable tissue.
Hotka, M., & Zahradnik, I. (2014). Membrane Capacitance Changes due to Temperature Increase in Rat Cardiac Myocytes. Biophysical Journal, 106(2), 121a–122a. https://doi.org/10.1016/j.bpj.2013.11.726