Activation of the nitric oxide/cGMP pathway is required for refilling intracellular Ca2+ stores in a sympathetic neuron cell line.
Fura-2 fluorescence imaging was used to measure changes in intracellular Ca2+ concentration in individual N1E-115 neuroblastoma cells during repeated activation of M1 muscarinic receptors with carbachol. Ca2+ transients could be elicited repeatedly at 4 min intervals with little decrement as long as external Ca2+ was present. When the cells were bathed in Ca(2+)-free saline, however, the response amplitude decreased rapidly in a use-dependent fashion, indicating that external Ca2+, and presumably Ca2+ influx, is required for refilling Ca2+ stores during the interval between trials. The response amplitude also decreased during repeated stimulation in cells treated with the NO-synthase inhibitor L-NMMA or with the guanylyl cyclase inhibitor LY-83583 even when Ca2+ was present. Application of the membrane permeable cGMP analog 8-Br-cGMP reversed the effect of L-NMMA and promoted refilling in the continued presence of NO-synthase inhibitor. These results indicate that activation of the NO/cGMP pathway is necessary for refilling Ca2+ stores during muscarinic signaling. Evidence is also presented suggesting that the NO/cGMP pathway is involved in long term modulation of the content of Ca2+ stores.
Harrington
M A
MA
Department of Biological Sciences, Stanford University, Pacific Grove, California, USA.
Thompson
S H
SH
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006157:Guanosine Monophosphate / Q000378:metabolism*; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000473:pathology; D014407:Tumor Cells, Cultured; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D006157:Guanosine Monophosphate; D019001:Nitric Oxide Synthase; D002118:Calcium