Na+ dependent Ca2+ influx induced by depolarization in neurons dissociated from rat nucleus basalis.
Neurons were acutely dissociated from the rat nucleus basalis, and whole-cell patch clamp recordings were made. Voltage dependent calcium currents (ICa) were recorded and fura-2 microfluorimetric recordings of intracellular free Ca2+ concentration ([Ca2+]i) were made at the same time. In Na(+)-containing solution, a depolarization from -60 to +40 mV evoked the maximal increase in [Ca2+]i, and this decreased to 43% of the maximal with a large depolarization to +120 mV. The [Ca2+]i increase induced by the large depolarization (+20 to +120 mV) was inhibited by perfusion of Na(+)-free external solution, and was less when the recording pipette contained a peptide (PRLLFYKYVYKRYRAGKQRG, named XIP) known to inhibit Na/Ca exchange. These results suggest that the [Ca2+]i increase by the large depolarization is mediated by reverse operation of Na/Ca exchange (Ca2+ inward and Na+ outward).
Tatsumi
H
H
Department of Autonomic Physiology, Tokyo Medical and Dental University, Japan.
Katayama
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016257:Fura-2; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology*; D013377:Substantia Innominata / Q000378:metabolism*
D012964:Sodium; D002118:Calcium; D016257:Fura-2