Calcium currents through the L-type voltage-sensitive calcium channel (L-VSCC) are increased in neurons of area CA1 of the hippocampus in aged rats and rabbits. Furthermore, increases in mRNA for the pore forming subunit alpha(1D) (Ca(v)1.3) have been observed in the hippocampus of aged rats. We have studied the protein expression of the two pore forming subunits, alpha(1C) (Ca(v)1.2) and alpha(1D), of L-VSCCs in the hippocampus of young and aged rats. Here we report selective age-related changes in expression of alpha(1D) in the hippocampus. Specifically, we find that alpha(1D) protein is increased in area CA1 of aged rats while it is decreased in area CA3. Our data suggest that the altered calcium currents seen in aged animals may be due, at least in part, to alterations in the expression of the alpha(1D) subunit of the L-type calcium channel. These findings contribute to our understanding of the mechanisms responsible for changes in calcium homeostasis during aging.