Nucleus tractus solitarius and excitatory amino acids in afferent-evoked inspiratory termination.
This study tested the hypothesis that excitatory amino acid (EAA) neurotransmission at non-N-methyl-D-aspartate (non-NMDA), but not NMDA, receptors within medial regions of the nucleus tractus solitarius (NTS) is required in the inspiratory termination elicited by vagal or intercostal nerve (ICN) stimulation. Adult cats were anesthetized, decerebrated, vagotomized, and ventilated. After control responses to stimulation of the superior laryngeal nerve (SLN), vagus, and ICN were obtained, EAA receptor antagonists were injected into the medial aspects of the NTS. Injections of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or 6,7-dinitro-quinoxaline-2,3-dione (DNQX), EAA receptor antagonists; (+/-)-2-amino-5-phosphonopentanoic acid (AP5), an NMDA antagonist; or 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), a non-NMDA antagonist, ipsilateral to the vagus abolished the termination response. The SLN-elicited response persisted after AP5 injection but was abolished by NBQX injections. The ICN-elicited response persisted after bilateral injections of CNQX/DNQX or procaine. We conclude that the inspiratory termination elicited by ICN stimulation is independent of the regions medial to the NTS. Inspiratory termination elicited by vagal or SLN stimulation requires non-NMDA-mediated EAA neurotransmission within medial aspects of the NTS, but the vagally elicited response also requires NMDA receptors.
Karius
D R
DR
Department of Physiology, University of Kentucky Medical Center, Lexington 40536-0084.
Ling
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Speck
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DF
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000596:Amino Acids / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002415:Cats; D003655:Decerebrate State / Q000503:physiopathology; D004558:Electric Stimulation; D005260:Female; D007367:Intercostal Nerves / Q000502:physiology; D007823:Laryngeal Nerves / Q000502:physiology; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D017552:Solitary Nucleus / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology
D015763:2-Amino-5-phosphonovalerate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000596:Amino Acids; D011810:Quinoxalines; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline