Nitric oxide modulates agonist-evoked Ca2+ release and influx responses in PC12-64 cells.
Nitric oxide (NO) is a signalling molecule involved in events crucial to neuronal cell function such as neurotransmitter release, gene transcription, and neurotoxicity. In these, as well as in many other neuronal processes, a key role may be played by the increases of the intracellular Ca2+ concentration ([Ca2+]i) occurring in response to activation of plasma membrane receptors coupled to phosphatidylinositol 4,5-bisphosphate hydrolysis. Such a [Ca2+]i increases are sustained by release of the cation from intracellular stores and stimulation of influx through specific Ca2+ channels. We have investigated the role of NO in modulating the two above Ca2+ processes occurring subsequently to muscarinic receptor activation in a selected clone (PC12-64) of PC12 cells, a neurosecretory/neuronal cell model. Analysis of [Ca2+]i variations in fura-2-loaded cells, exposed to different NO synthase inhibitors or NO donors, showed that Ca2+ release from intracellular stores was moderately inhibited and stimulated by these two groups of drugs, respectively, while Ca2+ influx through the channels directly coupled to muscarinic receptors was found to be insensitive to NO action. In contrast, Ca2+ influx activated by muscarinic receptor-induced store depletion (investigated also by Mn2+ quenching of the fura-2 signal) was increased by NO generation and inhibited by NO synthase blockade. Incubation of the cells with 8-bromo cGMP did not mimick the action of NO, suggesting that the effect of the messenger on Ca2+ influx is exerted through a signalling pathway different from cGMP generation.
Clementi
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Chair of Pharmacology, Faculty of Pharmacy, University of Reggio Calabria, Catanazaro, Italy.
Vecchio
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Corasaniti
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Nisticò
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D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006706:Homeostasis / Q000502:physiology; D018721:Muscarinic Agonists; D019331:NG-Nitroarginine Methyl Ester; D009474:Neurons / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D019001:Nitric Oxide Synthase; D009599:Nitroprusside / Q000494:pharmacology; D016716:PC12 Cells; D051381:Rats; D011976:Receptors, Muscarinic / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
D018721:Muscarinic Agonists; D011976:Receptors, Muscarinic; D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D006152:Cyclic GMP; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester