Abstract
Previous studies have shown that chronic intermittent hypoxia (CIH) induces sensory long‐term facilitation (sLTF) of the carotid body and augments LTF of phrenic nerve activity (pLTF). The present study was designed to examine whether sLTF plays a role in CIH‐induced potentiation of pLTF. Experiments were performed on male adult rats exposed to 10 days of normoxia or CIH. The effects of repetitive hypoxia (10 episodes of 15s hypoxia followed by 5min normoxia) were examined on efferent phrenic nerve activity and/or carotid body sensory activity in anesthetized, vagotomized, paralyzed, and mechanically ventilated rats. In the first series of experiments on CIH exposed rats (n=5), carotid body sensory activity was recorded along with efferent phrenic nerve activity. Repetitive hypoxia evoked robust pLTF and time course of the response paralled with carotid body sLTF. In the second series of experiments (n=6–8 rats each group), pLTF was examined in control, and CIH exposed rats with and without carotid body innervation. The magnitude of pLTF was significantly greater in CIH compared with control rats (p<0.05). Bilateral sectioning of the carotid sinus nerves immediately after terminating repetitive hypoxia attenuated pLTF in CIH rats (p<0.05). These results suggest that the carotid body sLTF contributes to augmented pLTF in CIH exposed rats. (Supported by NIH‐HL‐25830).
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