Nitric oxide raises cytosolic concentrations of Ca 2+ in cultured nodose ganglion neurons from rabbits

Abstract

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 Ca 2+ ([Ca 2+] i) were studied in cultured nodose ganglion neurons from newborn and young rabbits by loading with fura-2AM and microfluorometry. Application of SNAP (5 μM-1 mM) increased [Ca 2+] i in 46% of neurons tested. The threshold dose of the response was 10 μM and the response increased in a dose-dependent fashion. The increase in [Ca 2+] i at 50 μM averaged 74 ± 8% above the control value. [Ca 2+] i rose immediately after injection of SNAP and the plateau level was maintained in the presence of SNAP. NOR1, another donor of NO, increased [Ca 2+] i with an average increase of 82 ± 7% at 50 μM. 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 μM solution of NOR1. These data suggest that NO released from donors of NO induced an increase in [Ca 2+] i in nodose ganglion neurons and, therefore, that NO might play a role as a transmitter or a modulator in autonomic primary sensory systems.