Multiple calcium channel types control glutamatergic synaptic transmission in the hippocampus.
N-type calcium channels play a dominant role in controlling synaptic transmission in many peripheral neurons. Transmitter release from mammalian 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 omega-conotoxin and to omega-Aga-IVA, a P channel antagonist. Both toxins reduced the amplitude of excitatory postsynaptic potentials in CA1 pyramidal neurons, but omega-Aga-IVA was the more rapid and efficacious. These results were corroborated by biochemical studies measuring subsecond, calcium-dependent [3H]glutamate release from hippocampal synaptosomes. Thus, at least two calcium channel types trigger glutamate release from hippocampal neurons, but P-type plays a more prominent role. Eliminating synaptic transmission in the CNS, therefore, may require inhibiting more than a single calcium channel type.
Luebke
J I
JI
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Dunlap
K
K
Turner
T J
TJ
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D005971:Glutamates / Q000378:metabolism / Q000502:physiology*; D018698:Glutamic Acid; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013111:Spider Venoms / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005971:Glutamates; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D018698:Glutamic Acid; D020866:omega-Conotoxin GVIA