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The purpose of this study was to investigate the role of peripheral input, i.e. stimulation of superior laryngeal nerves (SLN), on the firing pattern of respiratory related nerves during fictive vomiting in cat. Decerebrate, paralyzed, and ventilated cats with successful FV induction were used in this experiment. Fictive vomiting (FV) was identified by a characteristic series of synchronous bursts in respiratory nerves (phrenic and abdominal nerves) induced by a prolonged electric stimulation on abdominal vagal afferents or by injection of emetic drugs such as apomorphine to the cat. Among 12 cats, 4 of them showed strong phrenic nerve (PHR) inhibition following SLN stimulation, most of the other cats showed minor inhibitory responses. The latency of the response was greater than 340 ms, similar to that from respiratory cats (160 to 340 ms). Spectral analysis indicated that the FV cat has high frequency oscillation (HFO) of 110 to 140 Hz occurred in their PHR neurogram while the same cat during respiratory had lower frequency oscillation (LFO) of 30 to 65 Hz in the neurogram. Stimulating the SLN inhibited only the HFO in FV cat. The spectrum at LFO (30 to 65 Hz) corresponding to commands from respiratory centers was not affected by SLN stimulation in the FV cat, but the LFO for respiratory cat was strongly inhibited by SLN stimulation. These results suggest that vomiting and respiration were controlled by separate central pattern generators, i.e. CPG-V and CPG-R respectively, even though they might have shared the same output motor apparatus.
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