Subthreshold aortic nerve inputs to neurons in nucleus of the solitary tract.
Subthreshold aortic nerve (AN) inputs to neurons receiving a monosynaptic AN-evoked input (MSNs: respond to each of two AN stimuli separated by 5 ms) and neurons receiving a polysynaptic AN input (PSNs) in the nucleus of the solitary tract (NTS) were identified in anesthetized rats. In extracellular recordings from 24 MSNs and 49 PSNs, 12% of MSNs and 29% of PSNs only responded to AN stimulation during the application of excitatory amino acids. In intracellular recordings from 24 MSNs and 22 PSNs, 12% of MSNs and 14% of PSNs responded to AN stimulation with excitatory postsynaptic potentials that did not evoke action potential discharge. Reductions in arterial pressure produced minimal changes in the spontaneous discharge of suprathreshold AN-evoked neurons, suggesting that these neurons receive excitatory inputs from nonbaroreceptor sources. The results suggest that some baroreflex-related NTS neurons exist in a "reserve state and can be changed to an active state or vice versa. This will change the number of neurons involved in baroreflex circuits and provides a novel mechanism for regulating baroreflex function independently of alterations in peripheral afferent input.
Zhang
J
J
Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7764, USA. ZHANGJ@UTHSCSA.edu
Mifflin
S W
SW
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000344:Afferent Pathways; D000818:Animals; D001011:Aorta / Q000294:innervation*; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000494:pharmacology; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D017552:Solitary Nucleus / Q000166:cytology* / Q000502:physiology*; D013268:Stimulation, Chemical; D013566:Sympathomimetics / Q000494:pharmacology; D013569:Synapses / Q000502:physiology; D014630:Vagus Nerve / Q000166:cytology* / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D013566:Sympathomimetics; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione