Coexistence of Functional IP3 and Ryanodine Receptors in Vagal Sensory Neurons and Their Activation by ATP

2002 
Intracellular photorelease of cagedd-myo-inositol 1,4,5-trisphosphate (IP3), caffeine application, and immunofluorescence confocal microscopy were used to determine thatd-myo-inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) coexist in rabbit vagal sensory nodose ganglion neurons (NGNs). ATP, an extracellular physiological signaling molecule, consistently evoked robust transient increases in cytosolic free Ca2+concentration (Ca2+ transients). ATP applied in Ca2+-free physiological saline elicited Ca2+ transients that averaged approximately 70% of the amplitude of transients evoked in the presence of extracellular Ca2+. The component of the ATP-evoked Ca2+ transient that was independent of extracellular Ca2+ corresponds to Ca2+ release from intracellular stores. This release component was sensitive to the pharmacological antagonists pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS), U73122, neomycin, and heparin (13.5–15 kD), indicating that P2 purinoreceptors (P2Y) ...
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