title: Nitric oxide inhibits the dopamine-induced K+ current via guanylate cyclase in Aplysia neurons.
abstract: Nitric oxide (NO) is produced by the enzyme nitric oxide synthase (NOS) and has been implicated in inter- and intracellular communication in the nervous system. The present study was undertaken to assess the effects of sodium nitroprusside (SNP) and hydroxylamine (HOA), NO donors, on a dopamine (DA)-induced K+ current in identified Aplysia neurons using voltage-clamp and pressure ejection techniques. Bath-applied SNP (10-25 microM) reduced the DA-induced K+ current without affecting the resting membrane conductance and holding current. The DA-induced K+ current also was inhibited by the focal application of 200 microM HOA to the neuron somata. The DA-induced K+ current suppressing effects of SNP and HOA are completely reversible. Pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 microM), a specific inhibitor of NO-stimulated guanylate cyclase, and hemoglobin (50 microM), a nitric oxide scavenger, decreased the SNP-induced inhibition of the DA-induced current. In contrast, intracellular injection of 1 mM guanosine 3',5'-cyclic monophosphate (cGMP) or bath-applied 3-isobutyl-1-methylxanthine (IBMX; 50 microM), a non-specific phosphodiesterase inhibitor, inhibited the DA-induced current, mimicking the effect of the NO donors. These results demonstrate that SNP and HOA inhibit the DA-induced K+ current and that the mechanism of NO inhibition of the DA-induced current involves cGMP-dependent protein kinase.
authors.affiliation: Department of Physiology, Shimane Medical University, Izumo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sawada
authors.forename: M
authors.initials: M
authors.lastname: Ichinose
authors.forename: G B
authors.initials: GB
authors.lastname: Stefano
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001048:Aplysia; D006152:Cyclic GMP / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000502:physiology*; D006162:Guanylate Cyclase / Q000378:metabolism*; D006454:Hemoglobins / Q000494:pharmacology; D019811:Hydroxylamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology*; D010069:Oxadiazoles / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D006454:Hemoglobins; D010069:Oxadiazoles; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011810:Quinoxalines; D009599:Nitroprusside; D019811:Hydroxylamine; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine; D004298:Dopamine