L-2-chloropropionic acid-induced cerebellar granule cell necrosis is potentiated by L-type calcium channel antagonists.

We have used the model of L-2-chloropropionic acid (L-CPA)-induced selective cerebellar granule necrosis to study excitatory amino acid-induced necrotic cell death in vivo produced by the activation of N-methyl-D-aspartate (NMDA) receptors. However, the mechanism for the NMDA receptor activation and the biochemical events which dictate the anatomical selectivity for the L-CPA-induced lesion are as yet unknown. We examined whether blockade of sodium and calcium channels may reduce the neurotoxicity through a reduction of glutamate release from granule cells. None of the sodium channel antagonists examined, i.e. phenytoin, lamotrigine or rilazole nor the mixed sodium/calcium channel blocker, lifarazine, altered the L-CPA neurotoxicity. However, L-type calcium channel blockers, verapamil and nifedipine enhanced the L-CPA-induced granule cell necrosis, assessed by measuring the degree of L-CPA-induced reductions in cerebellar aspartate concentration, increases in cerebellar glycine concentrations and the development of cerebellar oedema. In addition, the locomotor activity of rats receiving both L-CPA and either verapamil or nifedipine was significantly lower than when rats received L-CPA alone, suggesting an enhancement of the neurotoxicity of L-CPA by L-type calcium channel blockade. The data suggest that L-CPA may interfere with non-L-type calcium channels located on granule cell bodies and nerve terminals leading to reduction of the calcium entry into the cells. We suggest that a combination of L-type channel blockade and non-L-type channels which are sensitive to L-CPA produces reductions in intracellular calcium concentrations below that required for neuronal survival.