Hypoxia-induced long-term facilitation of respiratory activity is serotonin dependent.
Repeated isocapnic hypoxia evokes long-term facilitation (LTF) of phrenic nerve activity in rats. We wished to determine: (1) whether hypoxia-induced LTF is serotonin dependent; and (2) whether hypoxia-induced LTF is a property of upper airway motoneurons. Phrenic and hypoglossal nerve activities were recorded in urethane anesthetized, vagotomized, paralyzed and artificially ventilated rats (n = 7). Rats were exposed to three, 5-min hypoxic episodes (FIo2 = 0.10) separated by 5 min of hyperoxia (FIo2 = 0.50). One hour after the final hypoxic episode, integrated phrenic and hypoglossal amplitudes and burst frequency were increased above control values (63 +/- 17%, 78 +/- 26% and 9.6 +/- 2.1 bursts/min, respectively: p < 0.05). In rats pretreated with methysergide (n = 7; 4 mg/kg), no changes in phrenic or hypoglossal activity from pre-stimulus control values were observed at any time post-stimulation. The results indicate that hypoxia-induced LTF requires 5-HT receptors and is characteristic of both hypoglossal and phrenic motor output.
Department of Comparative Biosciences, University of Wisconsin, Madison 53706, USA.
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Bach
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Mitchell
D000768:Anesthesia, General; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D004558:Electric Stimulation; D007002:Hypoglossal Nerve / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D010791:Phrenic Nerve / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000502:physiology; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014628:Vagotomy
D012702:Serotonin Antagonists; D002245:Carbon Dioxide; D012701:Serotonin; D008784:Methysergide