Developmental change in the voltage-dependence of the pacemaker current, i_f, in rat ventricle cells

Abstract

 Myocytes were isolated from newborn and adult rat ventricle. Using the whole-cell patch clamp, the two cell populations were compared for the presence of the hyperpolarization-activated pacemaker current i_f. As in other mammalian species, the threshold voltage in acutely dissociated adult rat myocytes was extremely negative (–113 ± 5 mV; n=12). In contrast, threshold in newborn cells was relatively positive, regardless of whether measured in acutely dissociated (–72 ± 2 mV; n=6) or cultured cells (–70 ± 2 mV; n=9). Current density was not reduced in the adult. These results suggest that with development the ventricle assumes its non-pacemaker function, at least in part, by a shift of the voltage dependence of i_f outside the physiological range.