Phrenic long-term facilitation (pLTF) is a form of respiratory plasticity, manifested by prolonged increase in peak amplitude of phrenic nerve activity (PNA) after episodes of acute intermittent hypoxia (AIH). The aim was to investigate the effects of sevoflurane and isoflurane monoanesthesia at equipotent anesthetic doses on the expression of amplitude pLTF. Experiments were performed on Sprague-Dawley anesthetized, vagotomized, and mechanically ventilated rats. Two experimental groups, sevoflurane and isoflurane, and a control group (urethane-anesthetized) were formed. Peak amplitude of phrenic nerve activity, respiratory frequency and breathing rhythm parameters (Ti, inspiratory duration; Te, expiratory duration; and Ttot, total respiratory time duration) were analyzed during hypoxic episodes, and at 15, 30, and 60min after the last hypoxic episode. In the control group average PNA increased by 173.03±70.16% (p<0.001), at 60min after the last hypoxic episode compared to baseline values. Therefore amplitude pLTF was induced. In the sevoflurane and isoflurane groups PNA failed to increase, and in fact decreased by 15.79±15.18% and 31.00±11.00%, respectively (p>0.05). Amplitude pLTF was abolished during sevoflurane and isoflurane monoanesthesia.
Keywords: Intermittent hypoxia; Isoflurane; Phrenic nerve; Rat; Respiratory plasticity; Sevoflurane.
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