Effect of L-type calcium channel antagonists on spermine-induced CNS excitation in vivo

The ability of nitrendipine, nisoldipine, verapamil and gabapentin to inhibit the development of CNS excitation induced by spermine was assessed in mice. Injection of an excitotoxic dose of spermine (100 μg, i.c.v.) in mice results in worsening tremor that culminates in the development of a fatal tonic convulsion within 8 h of spermine administration. The dihydropyridines, nitrendipine and nisoldipine, which are L-type calcium channel antagonists acting at the α1 subunit, inhibited the development of spermine-induced effects. Verapamil, which also acts at the α1 subunit of the L-type calcium channel, also inhibited the development of spermine-induced CNS excitation. Gabapentin, a postulated L-type calcium channel antagonist interacting at the α2δ subunit, did not inhibit the development of spermine-induced effects. These results show that antagonists of the α1 subunit of L-type calcium channels can effectively inhibit the effects of spermine in vivo. This may highlight the importance of L-type calcium channels in spermine action.