Effects of nitric oxide and hypoxia on low-and high-voltage activated calcium currents in murine DRG neurons
The effects of a nitric oxide (NO)-containing aqueous solution (authentic NO) and hypoxia on low-and high-voltage activated calcium currents (I Ca,lva andI Ca,hva , respectively; in the latter transient and sustained portions were differentiated) were studied in enzymatically dispersed medium-sized neuronal somata from the murine dorsal root ganglia (DRG). Authentic NO (10 μM) was found to decrease the mean peak amplitude ofI Ca,lva , from 3.5±0.3 to 1.2±0.2 nA (n=11,p<0.001), as well as the amplitudes of transient and sustainedI Ca,hva components from 4.5±0.1 to 2.7±0.2 nA and form 2.8±0.2 to 1.7±0.2 nA (n=11;P<0.001), respectively. This NO-induced suppression was reversible and was removed by 1-min-long washout. At the same time, medium-sized DRG neurons demonstrated relatively low sensitivity to hypoxia (PO2=20–25 mm Hg): decreases of both types ofI Ca under hypoxic condition were not statistically significant (n=11;p>0.05). The data strongly suggest that NO is capable of reversibly suppressing both types of calcium channels in murine DRG neurons and of modulating in this way their excitability. It seems likely that this ability is based on a direct effect of NO on the corresponding channels and not on NO participation in the induction of hypoxic effects. Yet, a hypothesis that NO is a messenger of hypoxic damage to neural cells still should be suggested.
KeywordsNitric Oxide Dorsal Root Ganglion Tyrode Solution Nitric Oxide Concentration Sympathetic Preganglionic Neuron
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