Interaction of 1,4-dihydropyridines with somatic Ca currents in hippocampal CA1 neurones of the guinea pig in vitro.

Two distinct Ca currents may be recorded from guinea pig hippocampal CA1 neuronal somata: a non-inactivating (persistent) current and a rapidly inactivating (transient) current. Nimodipine, a 'calcium antagonist', reduced both Ca currents though the transient current was somewhat less sensitive than the persistent current. BAY K 8644, a 'calcium agonist' enhanced the persistent current and shifted the activation threshold for this current to more negative potentials. BAY K 8644 also enhanced the transient Ca current though the effect was very variable. The results demonstrate that Ca channels in hippocampal CA1 neurones possess a dihydropyridine receptor in common with Ca channels in other tissues.