Autoradiography of L-type and N-type calcium channels in aged rat hippocampus, entorhinal cortex, and neocortex.

The present study examined brains from 6, 17, and 32 month old male (F344x BN)F1 rats to determine whether there was any age-related change in the distribution or density of L-type and N-type Ca2+ channels in hippocampus, entorhinal cortex, and neocortex, areas commonly involved in the generation of epileptic seizures. The L-type channel antagonist PN200-110 and the N-type channel antagonist omega-conotoxin GVIA were used to determine specific binding densities and the autoradiographic distribution of ligand binding was quantified by computer-assisted densitometry. One-way ANOVA noted a significant variance in the mean value of binding density between different age groups only in neocortex laminae IV-VI for [(3)H]PN200-110 binding (P < 0.05). Post-hoc testing indicated that the mean value of the 17 month old group was significantly less than those of the 6 and 32 month old groups (P < 0.05). These results indicate no overall age-related change in the number of L-type and N-type Ca2+ channels in brain areas frequently involved in seizure activity and suggest that age-related changes in brain Ca2+ physiology may be associated with changes in voltage-gated Ca2+ channel function rather than channel number.