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[Effect of Hg2+ on voltage-dependent calcium channels and intracellular free calcium in trigeminal ganglion neurons of rats].

OBJECTIVE
To investigate the effects of Hg2+ on voltage-dependent calcium channels and intracellular free calcium in trigeminal ganglion neurons of rats and explore the toxicity mechanism of Hg2+ on these neurons.


METHODS
Whole cell patch-clamp technique was used to determine ICa of voltage-dependent calcium channels in trigeminal ganglion neurons of rats. Intracellular free calcium was measured to explore [Ca2+]i dynamic changes from a single cell level by laser scanning confocal microscopy and fluorescence probe techniques.


RESULTS
0.01, 0.10, 1.00 and 10.00 micromol/L Hg2+ could reduce voltage-dependent calcium channel currents ICa by (1.80+/-0.32)%, (23.04+/-9.46)%, (58.20+/-7.90)% and (82.00+/-5.77)% in trigeminal ganglion neurons. The inhibiting effects reached their maximum in 5 minutes and could not be reversed significantly during wash with Hg2+-free solution. Also, 0.01, 0.10 and 1.00 micromol/L Hg2+ increased intracellular free calcium concentrations by (2.50+/-0.83)%, (82.81+/-35.36)% and (222.70+/-62.48)% in trigeminal ganglion neurons. Pre-administrated trigeminal ganglion neurons with nifedipine for 10 minutes could decrease the effects and delay the effecting time.


CONCLUSION
The inhibition of Hg2+ on the voltage-dependent calcium channel currents ICa depends on voltage-dependent calcium channels. And the increase of intracellular free calcium concentration in trigeminal ganglion neurons induced by Hg2+ is related to the release of intracellular stored calcium. However, the relationship between them needs further investigation.