Dibutyryl cGMP raises cytosolic concentrations of Ca in cultured nodose ganglion neurons of the rabbit

The effect of dibutyryl cGMP (dbcGMP), a membrane permeant cGMP analogue, on cytosolic concentrations of Ca²⁺ ([Ca²⁺]_i) was studied in cultured nodose ganglion neurons of the rabbit using fura-2AM and microfluorometry. Application of dbcGMP (10–1000 μM) increased [Ca²⁺]_i in 42% of neurons (n=67). The effect was observed in a dose-dependent fashion. The threshold dose was 100 μM and the increase at 500 μM averaged 117±8%. Removal of extracellular Ca²⁺ abolished the dbcGMP effect. Application of Ni²⁺ (1 mM) or neomycin (50 μM), a non-L-type voltage-gated Ca²⁺ channel (VGCC) antagonist, eliminated the dbcGMP effect. ω-conotoxin GVIA (2 μM), the N-type Ca²⁺ channel antagonist, or L-type Ca²⁺ channel antagonists (D600, 50 μM, or nifedipine, 10 μM) did not alter the dbcGMP effect. Ryanodine (10 μM) did not alter the effect of dbcGMP. Therefore, cGMP could play a part of role of an intracellular messenger in primary sensory neurons of the autonomic nervous system.