Either N- or P-type calcium channels mediate GABA release at distinct hippocampal inhibitory synapses.
Transmitter release at most central synapses depends on multiple types of calcium channels. Identification of the channels mediating GABA release in hippocampus is complicated by the heterogeneity of interneurons. Unitary IPSPs were recorded from pairs of inhibitory and pyramidal cells in hippocampal slice cultures. The N-type channel antagonist omega-conotoxin MVIIA abolished IPSPs generated by interneurons in st. radiatum, whereas the P/Q-type antagonist omega-agatoxin IVA had no effect. In contrast, omega-agatoxin IVA abolished IPSPs generated by st. lucidum and st. oriens interneurons, but omega-conotoxin MVIIA had no effect. After unitary IPSPs were blocked by toxin, transmission could not be restored by increasing presynaptic calcium entry. The axons of the two types of interneurons terminated within distinct strata of area CA3. Thus, GABA release onto pyramidal cells, unlike glutamate release, is mediated entirely by either N- or P-type calcium channels, depending on the presynaptic cell and the postsynaptic location of the synapse.
Poncer
J C
JC
Brain Research Institute, University of Zurich, Switzerland.
McKinney
R A
RA
Gähwiler
B H
BH
Thompson
S M
SM
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007395:Interneurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D013111:Spider Venoms / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018691:Excitatory Amino Acid Antagonists; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; C053157:omega-conotoxin receptor; D005680:gamma-Aminobutyric Acid; C078452:ziconotide; D020866:omega-Conotoxin GVIA; D002118:Calcium