Synaptic inputs onto spiking local interneurons in crayfish are depressed by nitric oxide.
We have analyzed the action of nitric oxide on the synaptic inputs of spiking local interneurons that form part of the local circuits in the terminal abdominal ganglion of the crayfish, Pacifastacus leniusculus. Increasing the availability of NO in the ganglion by bath applying the NO donor SNAP, or the substrate for its synthesis, L-arginine, caused a depression of synaptic inputs onto the interneurons evoked by electrically stimulating mechanosensory neurons in nerve 2 of the terminal ganglion. Conversely, reducing the availability of NO by bath application of an NO scavenger, PTIO, and an inhibitor of nitric oxide synthase, L-NAME, increased the amplitude of the evoked potentials. These results suggest that elevated NO concentration causes a depression of the synaptic inputs to spiking local interneurons. To determine whether these effects could be mediated through an NO/cGMP signaling pathway we bath applied a membrane permeable analogue of cGMP, 8-br-cGMP, which decreased the amplitude of the inputs to the interneurons. Bath application of an inhibitor of soluble guanlylyl cyclase, ODQ, produced an increase in the amplitude of the synaptic inputs. Our results suggest that NO causes a depression of synaptic inputs to spiking local interneurons probably by acting through an NO/cGMP signaling pathway. Moreover, application of NO scavengers modulates the inputs to these interneurons, suggesting that NO is continuously providing a powerful and dynamic means of modulating the outputs of local circuits.
School of Biological Sciences, University of Southampton, Biomedical Sciences Building, Bassett Crescent East, Southampton SO16 7PX, United Kingdom.
Hitoshi
H
Aonuma
Philip L
PL
Newland
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003400:Astacoidea; D006152:Cyclic GMP / Q000378:metabolism; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007395:Interneurons / Q000502:physiology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009475:Neurons, Afferent / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000502:physiology*
D003497:Cyclic N-Oxides; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D020030:Nitric Oxide Donors; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D001120:Arginine; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester