Nitric oxide raises cytosolic concentrations of Ca2+ in cultured nodose ganglion neurons from rabbits.

The effects of donors of nitric oxide (NO), namely, S-nitroso-N-acetylpenicillamine-(SNAP) and E-methyl-2-E-hydroxyimino-5-nitro-6-methoxy-3-hexeneamide (NOR1), on cytosolic concentrations of Ca2+ ([Ca2+]i) were studied in cultured nodose ganglion neurons from newborn and young rabbits by loading with fura-2AM and microfluorometry. Application of SNAP (5 microM-1 mM) increased [Ca2+]i in 46% of neurons tested. The threshold dose of the response was 10 microM and the response increased in a dose-dependent fashion. The increase in [Ca2+]i at 50 microM averaged 74 +/- 8% above the control value. [Ca2+]i rose immediately after injection of SNAP and the plateau level was maintained in the presence of SNAP.NOR1, another donor of NO, increased [Ca2+]i with an average increase of 82 +/- 7% at 50 microM. Quantitation of NO gas in the solution of NOR1 by a redox chemiluminescence method revealed the constant release of 0.06 ppm NO from 5 ml of a 20 microM solution of NOR1. These data suggest that NO released from donors of NO induced an increase in [Ca2+]i in nodose ganglion neurons and, therefore, that NO might play a role as a transmitter or a modulator in autonomic primary sensory systems.