Transient rise in intracellular calcium produces a long-lasting increase in plasma membrane calcium pump activity in rat sensory neurons.
The plasma membrane Ca2+ ATPase (PMCA) plays a major role in clearing Ca2+ from the neuronal cytoplasm. Calmodulin stimulates PMCA activity and for some isoforms this activation persists following clearance of Ca2+ owing to the slow dissociation of calmodulin. We tested the hypothesis that PMCA-mediated Ca2+ efflux from rat dorsal root ganglion (DRG) neurons in culture would remain stimulated following increases in intracellular Ca2+ concentration ([Ca2+]i). PMCA-mediated Ca2+ extrusion was recorded following brief trains of action potentials using indo-1-based photometry in the presence of cyclopiazonic acid. A priming stimulus that increased [Ca2+]i to 506 +/- 28 nm (>15 min) increased the rate constant for [Ca2+]i recovery by 47 +/- 3%. Ca2+ clearance from subsequent test stimuli remained accelerated for up to an hour despite removal of the priming stimulus and a return to basal [Ca2+]i. The acceleration depended on the magnitude and duration of the priming [Ca2+]i increase, but was independent of the source of Ca2+. Increases in [Ca2+]i evoked by prolonged depolarization, sustained trains of action potentials or activation of vanilloid receptors all accelerated Ca2+ efflux. We conclude that PMCA-mediated Ca2+ efflux in DRG neurons is a dynamic process in which intense stimuli prime the pump for the next Ca2+ challenge.
Pottorf
William J
WJ
Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
Thayer
Stanley A
SA
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000166:cytology; D007424:Intracellular Fluid / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011955:Receptors, Drug / Q000378:metabolism
D011955:Receptors, Drug; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002211:Capsaicin; D002118:Calcium