Carbamazepine inhibits L-type Ca2+ channels in cultured rat hippocampal neurons stimulated with glutamate receptor agonists

Abstract

In order to better understand the mechanism(s) of action of carbamazepine (CBZ), we studied its effects on the increase in [Ca 2 + ] i and [Na + ] i stimulated by glutamate ionotropic receptor agonists, in cultured rat hippocampal neurons, as followed by indo-1 or SBFI fluorescence, respectively. CBZ inhibited the increase in [Ca 2 + ] i stimulated either by glutamate, kainate, a-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA), or N-methyl-D-aspartate (NMDA), in a concentration-dependent manner. In order to discriminate the effects of CBZ on the activation of glutamate receptors from possible effects on Ca 2 + channels, we determined the inhibitory effects of Ca 2 + channel blockers on [Ca 2 + ] i changes in the absence or in the presence of CBZ. The presence of 1 mM nitrendipine, 0.5 mM v-conotoxin GVIA (v-CgTx GVIA), or of both blockers, inhibited the kainate-stimulated increase in [Ca 2 + ] i by 51.6, 32.9 or 68.7%, respectively. In the presence of both 100 mM CBZ and nitrendipine, the inhibition was similar (54.1%) to that obtained with nitrendipine alone, but in the presence of both CBZ and v-CgTx GVIA, the inhibition was greater (54%) than that caused by v-CgTx GVIA alone. However, CBZ did not inhibit the increase in [Na + ] i stimulated by the glutamate receptor agonists, but inhibited the increase in [Na + ] i due to veratridine. Tetrodotoxin, or MK-801, did not inhibit the influx of Na + stimulated by kainate, indicating that Na + influx occurs mainly through the glutamate ionotropic non-NMDA receptors. Moreover, LY 303070, a specific AMPA receptor antagonist, inhibited the [Na + ] i response to kainate or AMPA by about 70 or 80%, respectively, suggesting that AMPA receptors are mainly involved. Taken together, the results suggest that CBZ inhibits L-type Ca 2 + channels and Na + channels, but does not inhibit activation of glutamate ionotropic receptors.

Review: Is levetiracetam different from other antiepileptic drugs? Levetiracetam and its cellular mechanism of action in epilepsy revisited

“…Calcium entering through L-type calcium channels may play a role in activity-dependent gene expression and synaptic plasticity. Some AEDs (such as carbamazepine) have been proposed to antagonise L-type calcium channels but the relevance of this to their antiepileptic effect is unclear [Ambrosio et al 1999]. N-and P/Q-type channels are expressed at synaptic boutons where they mediate calcium entry necessary for neurotransmitter release.…”

Purinergic P2 receptors trigger adenosine release leading to adenosine A2A receptor activation and facilitation of long-term potentiation in rat hippocampal slices

“…Hippocampal neurons were dissociated from hippocampi of E18 -E19 rat embryos, as previously described (Ambró sio et al, 1999) and cultured in serum free Neurobasal medium (GIBCO, Life Technologies, UK) with B27 supplement (GIBCO), 25 M glutamine, 0.5 mM glutamate and 0.12 mg/ml gentamicin. Cultures were plated on poly-D-lysine-coated (0.1 mg/ml) glass coverslips at a density of 0.2ϫ10 6 cells/cm 2 and kept at 37°C in a humidified incubator in 5% CO 2 /95% air for 7-8 days, the time required for maturation of hippocampal neurons.…”

Differential Contribution of L-, N-, and P/Q-type Calcium Channels to [Ca2+]i Changes Evoked by Kainate in Hippocampal Neurons

“…We have previously shown that VSCCs, mainly L-and N-type Ca 2+ channels, have a predominant role in the [Ca 2+ ] i changes evoked by kainate in cultured hippocampal neurons measured in cell populations [13]. The [Ca 2+ ] i responses evoked by kainate have a high degree of variability among individual hippocampal neurons [14], which is likely due to a differential expression of AMPA and kainate receptors.…”