Modulation of spectral dynamics in inspiratory motor discharges during breath‐witholding in urethane‐anesthetized adult rat in vivo

Abstract

Input from vagal lung afferents participates in the regulation of breath-to-breath inspiratory depth and duration. Although numerous studies have examined timing and magnitude changes associated with no inflation and/or hyperinflation maneuvers, little is known about the influence of lung afferent input on inspiratory-phase spectral activity and its dynamics. Therefore, we used the no inflation test to examine the role of lung afferent input on time-frequency (TF) spectral activity in phrenic nerve discharge in urethane-anesthetized adult rats in vivo. For these experiments, the no inflation test consisted of 2–7 trials of withholding 5 breaths (i.e., pausing mechanical ventilation), which resulted in a progressive increase in phrenic burst amplitude and duration (TI). Evaluation of ensemble-averaged TF spectra for each individual trial and for all trials conducted in individual rats revealed a variety of TF spectrum activity patterns during breath withholding; however, hints of increased spectral power, increased spectral frequencies, and reduced spectral duration were observed. Reexamination of ensemble-averaged TF spectra for each breath across trials revealed a more concentrated distribution of spectral activity at the 3rd or 4th withheld breath. These findings suggest that elimination of lung afferent input by breath withholding results in reconfiguration of the inspiratory network to enhance inspiratory-phase synchronization. Supported by NS045321, NS049310, and The APS Undergraduate Summer Research Fellowship Program