Phrenic long-term facilitation requires 5-HT receptor activation during but not following episodic hypoxia

Episodic hypoxia evokes a sustained augmentation of respiratory motor output known as long-term facilitation (LTF). Phrenic LTF is prevented by pretreatment with the 5-hydroxytryptamine (5-HT) receptor antagonist ketanserin. We tested the hypothesis that 5-HT receptor activation is necessary for the...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2001-05, Vol.90 (5), p.2001-6; discussion 2000
Main Authors: Fuller, D D, Zabka, A G, Baker, T L, Mitchell, G S
Format: Article
Language:English
Subjects:
Animals
Hypoxia - physiopathology
Ketanserin - pharmacology
Male
Neuronal Plasticity - drug effects
Neuronal Plasticity - physiology
Phrenic Nerve - drug effects
Phrenic Nerve - physiology
Phrenic Nerve - physiopathology
Rats
Rats, Sprague-Dawley
Receptors, Serotonin - physiology
Respiratory Mechanics - physiology
Serotonin Antagonists - pharmacology
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Summary:Episodic hypoxia evokes a sustained augmentation of respiratory motor output known as long-term facilitation (LTF). Phrenic LTF is prevented by pretreatment with the 5-hydroxytryptamine (5-HT) receptor antagonist ketanserin. We tested the hypothesis that 5-HT receptor activation is necessary for the induction but not maintenance of phrenic LTF. Peak integrated phrenic nerve activity (integralPhr) was monitored for 1 h after three 5-min episodes of isocapnic hypoxia (arterial PO(2) = 40 +/- 2 Torr; 5-min hyperoxic intervals) in four groups of anesthetized, vagotomized, paralyzed, and ventilated Sprague-Dawley rats [1) control (n = 11), 2) ketanserin pretreatment (2 mg/kg iv; n = 7), and ketanserin treatment 0 and 45 min after episodic hypoxia (n = 7 each)]. Ketanserin transiently decreased integralPhr, but it returned to baseline levels within 10 min. One hour after episodic hypoxia, integralPhr was significantly elevated from baseline in control and in the 0- and 45-min posthypoxia ketanserin groups. Conversely, ketanserin pretreatment abolished phrenic LTF. We conclude that 5-HT receptor activation is necessary to initiate (during hypoxia) but not maintain (following hypoxia) phrenic LTF.
ISSN:8750-7587