Opposite effects of nitric oxide on identified inhibitory and excitatory cholinergic synapses of Aplysia californica.
The effects of nitric oxide on evoked acetylcholine (ACh) release were studied at two identified cholinergic neuro-neuronal synapses of the nervous system of the mollusc Aplysia californica. The NO-donor, 3-morpholinosydnonimine (SIN-1), decreased the amplitude of evoked inhibitory postsynaptic currents (buccal ganglion) and potentiated that of evoked excitatory postsynaptic currents (abdominal ganglion). SIN-1 acted by modulating the number of ACh quanta released. 8Br-cGMP mimicked the effects of NO on ACh release in both types of synapses thus pointing to the involvement of a NO-sensitive guanylate cyclase. Presynaptic voltage-dependent Ca2+ and K+ (IA and late outward rectifier) currents were not modified by SIN-1 suggesting another final target for NO/cGMP. The labelling of a NO-synthase by immunostaining in several neurones as well as the modulation of ACh release by L-arginine indicate that an endogenous NO-synthase is involved in the modulation of synaptic efficacy in both buccal and abdominal ganglia.
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Laboratoire de Neurobiologie Cellulaire et Moléculaire C.N.R.S., Gif-sur-Yvette, France.
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D000109:Acetylcholine / Q000378:metabolism* / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D001048:Aplysia; D001120:Arginine / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000187:drug effects / Q000378:metabolism; D005726:Ganglia, Parasympathetic / Q000187:drug effects* / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects; D013569:Synapses / Q000187:drug effects* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*
D015220:Calcium Channels; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D015221:Potassium Channels; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; C002385:linsidomine; D001120:Arginine; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D000109:Acetylcholine