MULTIPLE CALCIUM-CHANNEL TYPES CONTROL GLUTAMATERGIC SYNAPTIC TRANSMISSION IN THE HIPPOCAMPUS

N-type calcium channels play a dominant role in controlling synaptic t ransmission in many peripheral neurons. Transmitter release from mamma lian central nerve terminals, however, is relatively resistant to the N channel antagonist omega-conotoxin GVIA. We studied the sensitivity of glutamatergic synaptic transmission in rat hippocampal slices to om ega-conotoxin and to omega-Aga-IVA, a P channel antagonist. Both toxin s reduced the amplitude of excitatory postsynaptic potentials in CA1 p yramidal neurons, but omega-Aga-IVA was the more rapid and efficacious . These results were corroborated by biochemical studies measuring sub second, calcium-dependent [H-3]glutamate release from hippocampal syna ptosomes. Thus, at least two calcium channel types trigger glutamate r elease from hippocampal neurons, but P-type plays a more prominent rol e. Eliminating synaptic transmission in the CNS, therefore, may requir e inhibiting more than a single calcium channel type.