Gabapentin blocks L-type and P/Q-type Ca2+ channels involved in depolarization-stimulated nitric oxide synthase activity in primary cultures of neurons from mouse cerebral cortex.

PURPOSE

The effect of gabapentin [1-(aminomethyl)cyclohexane acetic acid] on Ca2+ channels involving the activation of nitric oxide synthase (NOS) was investigated in primary neuronal culture of mouse cerebral cortex.

METHODS

The expression of alpha2delta subunits of Ca2+ channels was investigated by RT-PCR using specific primer sets. The K(+)-evoked NOS activity was estimated by guanosine 3'5' cyclic monophosphate (cGMP) formation.

RESULTS

mRNA for alpha2delta subunits of Ca2+ channels is found in these cells. Gabapentin blocked the K(+)-evoked NOS activity estimated from cGMP formation in a concentration dependent manner. The increase in NOS activity by the K(+)-stimulation was almost completely reversed by the combination of nifedipine, an L-type Ca2+ channel blocker, and omega-agatoxin VIA, a P/Q-type Ca2+ channel blocker. On the other hand, omega-conotoxin GVIA, an N-type Ca2+ channel blocker, was failed to reverse the increase in NOS activity by the K(+)-stimulation, indicating that the activation of NOS by the depolarizing stimulation might be not mediated by N-type Ca2+ channel. Under the presence of nifedipine or omega-agatoxin IVA, gabapentin inhibited the increase in NOS activity concentration-dependently.

CONCLUSIONS

These results suggest that gabapentin inhibits depolarization-induced NOS activation in murine cortical neuronal culture via blockade of both P/Q-type and L-type Ca2+ channels.