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.
OBJECTIVE
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.
Oka
Michiko
M
Department of Biochemical Pharmacology, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
Itoh
Yoshinori
Y
Wada
Miyuki
M
Yamamoto
Akira
A
Fujita
Takuya
T
D000085:Acetates / Q000494:pharmacology*; D000588:Amines; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D020865:Calcium Channels, P-Type / Q000187:drug effects*; D020907:Calcium Channels, Q-Type / Q000187:drug effects*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D006152:Cyclic GMP / Q000096:biosynthesis; D003509:Cyclohexanecarboxylic Acids; D005260:Female; D000077206:Gabapentin; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D009543:Nifedipine / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D052248:Nitric Oxide Synthase Type I; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D005680:gamma-Aminobutyric Acid; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D000085:Acetates; D000588:Amines; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D003509:Cyclohexanecarboxylic Acids; D012333:RNA, Messenger; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D000077206:Gabapentin; D020866:omega-Conotoxin GVIA; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; D006152:Cyclic GMP; D009543:Nifedipine