Transmitter release and calcium currents at an Aplysia buccal ganglion synapse--I. Characterization.
The Ca2+ current recorded in the presynaptic neuron (B4/B5) of an identified Aplysia synapse was characterized in terms of its activation, voltage sensitivity, Ca2+ dependence of inactivation and pharmacology. It was compared to that recorded in left upper quadrant abdominal ganglion neurons which, unlike B4/B5, display Ca2+ action potentials. The two Ca2+ currents could not be distinguished in terms of their activation threshold or voltage sensitivity. The Ca2+ current recorded in left upper quadrant neurons, however, displayed more important Ca(2+)-dependent inactivation. The peak Ca2+ current in B4/B5 neurons was significantly reduced (30-40%) by the dihydropyridine Ca2+ channel antagonist, nifedipine, while it was increased (15-20%) by the dihydropyridine Ca2+ channel agonist, BAY K8644, although none of these agents had any effect on transmitter release from B4/B5. omega-Conotoxin similarly reduced the Ca2+ current by 30-40%, but unlike nifedipine, it also caused a 50-60% reduction in B4/B5 transmitter release. The pharmacological properties of the Ca2+ current present in left upper quadrant neurons were somewhat different, as this current was unaffected by either BAY K8644 or omega-conotoxin and moderately suppressed (20%) by nifedipine.
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Laboratoire de Neurobiologie Cellulaire et Moléculaire, C.N.R.S., Gif-sur-Yvette, France.
Baux
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Fossier
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Tauc
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D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D004594:Electrophysiology; D005724:Ganglia / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018377:Neurotransmitter Agents; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; C053423:Conus magus toxin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine