Research article
Hypoxia-induced long-term facilitation of respiratory activity is serotonin dependent

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Abstract

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.

References (27)

  • J.T. Erickson et al.

    Hypoxia and electrical stimulation of the carotid sinus nerve induce Fos-like immunoreactivity within catecholamine and serotonergic neurons of the rat brainstem

    J. Compar. Neurol.

    (1994)
  • R. Fregosi et al.

    Long term facilitation of inspiratory intercostal nerve activity following repeated carotid sinus nerve stimulation in cats

    J. Physiol. (London)

    (1994)
  • F. Hayashi et al.

    Time dependent phrenic nerve responses to carotid afferent activation: intact vs decerebellate rats

    J. Physiol. (London)

    (1993)
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