Sodium nitroprusside blocks the cat carotid chemosensory inhibition induced by dopamine, but not that by hyperoxia.
We studied the effects of the nitric oxide (NO) synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME), and the NO donor, sodium nitroprusside (SNP) on cat chemosensory responses to intravenous injections of NaCN (0.1-100 microg/kg) and dopamine (0. 1-20 microg/kg), and to hyperoxic ventilation (100% O2, 60-120 s). Cats were anesthetized with sodium pentobarbitone, paralyzed and artificially ventilated to prevent secondary ventilatory effects. The frequency of chemosensory discharges (fx) was recorded from one sectioned carotid sinus nerve. L-NAME (50 mg/kg i.v.) increased basal fx and slightly potentiated the responses to NaCN and dopamine. SNP (1-2 mg/kg i.v.) increased basal fx, but reduced the NaCN-induced increases of fx over baseline and the transient fx inhibitions induced by dopamine, but not those produced by hyperoxia. Present results indicate that besides the known inhibitory effect of NO on chemosensory responses to low PO2, NO also blocks the chemosensory response to dopamine, leaving hyperoxic responses largely unchanged.
Laboratory of Neurobiology, Faculty of Biological Sciences, P. Catholic University of Chile, Casilla 114-D, Santiago 1, Chile. riturria@genes.bio.puc.cl
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Iturriaga
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Alcayaga
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Rey
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002339:Carotid Arteries / Q000294:innervation*; D002415:Cats; D002628:Chemoreceptor Cells / Q000187:drug effects*; D004298:Dopamine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018496:Hyperoxia / Q000503:physiopathology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D012966:Sodium Cyanide / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009599:Nitroprusside; D012966:Sodium Cyanide; D019331:NG-Nitroarginine Methyl Ester; D004298:Dopamine