title: Inhibition of the glutamate-induced K(+) current in identified Onchidium neurons by nitric oxide donors.
abstract: Nitric oxide (NO) acts as a neurotransmitter and neuromodulator in the nervous system of many vertebrates and invertebrates. The effects of extracellularly applied sodium nitroprusside (SNP) and diethylamine NO (C(2)H(5))(2)N[N(O)NO]-Na(+) (DEA/NO), NO donors, on a glutamate (Glu)-induced K(+) current in identified Onchidium neurons were investigated using voltage clamp and pressure ejection techniques. Bath-applied SNP (10 microM) and DEA/NO (5-10 microM) reduced the Glu-induced K(+) current without affecting the resting membrane conductance and holding current. The Glu-induced K(+) current also was inhibited by the focal application of SNP to the neuron somata. The suppressing effects of NO donors were concentration-dependent and completely reversible. Pretreatment with hemoglobin (50 microM), a nitric oxide scavenger, and 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 microM), a specific inhibitor of NO-stimulated guanylate cyclase, decreased the SNP-induced inhibition of the Glu-induced current. Bath-applied 50 microM 3-isobutyl-1-methylxanthine (IBMX), a nonspecific phosphodiesterase inhibitor, or intracellular injection of 1 mM guanosine 3',5'-cyclic monophosphate (cGMP) inhibited the Glu-induced current, mimicking the effect of NO donors. These results demonstrate that SNP and DEA/NO inhibit the Glu-induced K(+) current and that the mechanism of NO inhibition of the Glu-induced current involves cGMP-dependent protein kinase.
authors.affiliation: Department of Physiology, Shimane Medical University, Izumo, Japan. msawada@shimane-med.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Sawada
authors.forename: M
authors.initials: M
authors.lastname: Ichinose
authors.forename: M
authors.initials: M
authors.lastname: Anraku
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018698:Glutamic Acid / Q000187:drug effects* / Q000378:metabolism* / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D008974:Mollusca; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009589:Nitrogen Oxides; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D006834:Hydrazines; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D010069:Oxadiazoles; D010726:Phosphodiesterase Inhibitors; D015221:Potassium Channels; D011810:Quinoxalines; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; D018698:Glutamic Acid; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine