Systemic hypoxia facilitates somato-cardiac sympathetic A- and C-reflexes in anesthetized rats.
In rats anesthetized with urethane, electrical stimuli applied to tibial nerve afferents produced a somato-sympathetic A-reflex of 41 +/- 2 (mean +/- SEM)ms latency and C-reflex of 210 +/- 13 ms latency recorded in the left inferior cardiac sympathetic nerve. Hypoxia was induced by switching room air to nitrogen/oxygen gas mixture in the inspiratory line reducing end-tidal oxygen from about 18% FETO2 to 10% FETO2 and 6% FETO2 for 60s, respectively. During 6% FETO2 hypoxia, the amplitude of the somato-cardiac sympathetic A-reflex increased significantly to 138 +/- 13% of the control, and that of the C-reflex increased to 186 +/- 18% of the control. During 10% FETO2 hypoxia, the A-reflex increased insignificantly to 117 +/- 8%; the amplitude of the C-reflex was augmented significantly to 149 +/- 11% of the control. Peripheral carotid chemoreceptor denervation abolished the facilitatory effects of systemic hypoxia. It is concluded that carotid chemoreceptor stimulation enhances the responsiveness of somato-cardiac sympathetic excitatory reflexes originating in the hind limb receptors.
Department of the Autonomic Nervous System, Tokyo Metropolitan Institute of Gerontology, Japan.
W M
WM
Li
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A
Sato
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A
Suzuki
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Trzebski
D000818:Animals; D002346:Carotid Sinus / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D006614:Hindlimb; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology