L-type voltage-sensitive calcium channel antagonists block heterosynaptic long-term depression in the dentate gyrus of anaesthetized rats.

We examined the role of dihydropyridine-sensitive Ca2+ channels in long-term potentiation (LTP) and long-term depression (LTD) in the dentate gyrus of pentobarbital-anaesthetized rats. Intrahippocampal infusions (1.0 microliter) of nimodipine (20 mM) and nifedipine (20 mM), two antagonists of L-type voltage-sensitive calcium channels (VSCC), 60 min prior to medial perforant path tetanization, completely blocked the appearance of LTD in the lateral perforant path, without significantly affecting the simultaneous induction of medial path LTP. Heterosynaptic LTD was not significantly different from control animals following infusions of the L-type calcium channel agonist BAY-K8644 (1 mM). These results suggest that L-type VSCC activity is necessary for the induction of heterosynaptic LTD in the dentate gyrus in vivo.