부산대학교 도서관

Summary We investigated the effect of changes in membrane‐voltage on intracellular sodium concentration ([Na+ ]i ) of dopamine‐sensitive neurons of the substantia nigra pars compacta in a slice preparation of rat mesencephalon. Whole‐cell patch‐clamp techniques were combined with microfluorometric measurements of [Na+ ]i using the Na+ ‐sensitive probe, sodium‐binding benzofuran isophthalate (SBFI). Hyperpolarization of spontaneously active dopamine neurons (recorded in current‐clamp mode) caused the cessation of action potential firing accompanied by an elevation in [Na+ ]i . In dopamine neurons voltage‐clamped at a holding potential of –60 mV elevations of [Na+ ]i were induced by long‐lasting (45–60 s) voltage jumps to more negative membrane potentials (–90 to –120 mV) but not by corresponding voltage jumps to –30 mV. These hyperpolarization‐induced elevations of [Na+ ]i were depressed during inhibition of Ih , a hyperpolarization‐activated inward current, by Cs+ . Hyperpolarization‐induced elevations in [Na+ ]i might occur also in other cell types which express a powerful Ih and might signal lack of postsynaptic activity. [ABSTRACT FROM AUTHOR]