Power spectral analysis of inspiratory nerve activity in the anesthetized rat: uncorrelated fast oscillations in different inspiratory nerves.

The spectral composition of the inspiratory nerve discharge was studied in spontaneously breathing Sprague-Dawley rats under urethane (n = 7) or barbiturate (n = 10). Left phrenic nerve activity was recorded simultaneously with right phrenic or left recurrent laryngeal nerves. We found that all neurograms showed prominent fast oscillators at common frequencies in the high frequency (HFO) range. Concurrent medium frequency oscillations (MFO) were present in inspiratory nerve discharges of four rats anesthetized with Nembutal. Significant coherences between nerves were uncommon (n = 2) and were only found between HFOs. Thus although nerve autospectra were dominated by HFO, weak correlations indicated a relatively weak system HFO in th central pattern generator, in the anesthetized rat.