Characterization of fast oscillatory rhythms in multiple respiratory‐related motor outputs during eupnea in decerebrate adult rat in vivo

Abstract

Respiratory motor discharges exhibit both slow and fast oscillatory rhythms. The slow rhythms correspond to inspiratory (I), expiratory (E), or phase‐spanning behaviors while the fast rhythms appear to be exclusive to motor outputs exhibiting inspiratory‐related discharges. To further evaluate these respiratory‐related rhythms, we examined basal phrenic (PHR), hypoglossal (XII), and recurrent laryngeal (RLN) nerve bursts recorded simultaneously from decerebrate (unanesthetized) paralyzed mechanically‐ventilated adult rats in vivo. PHR discharge served as an index of I activity, and burst duration (TI) and the duration between bursts (TE) were determined from PHR traces. XII activity exhibited pre‐I and I phase discharge and RLN activity exhibited pre‐I, I, and E phase discharge. In each respiratory‐related motor output, high frequency oscillations (HFO) were identified but they were restricted to the I phase of each burst (i.e., no significant HFO activity was seen during pre‐I or E phases). PHR and RLN HFO peaks were located between 100‐150 Hz, and XII activity exhibited several distinct peaks with a broadband power distribution. HFO onset occurred at ~50% TI for PHR activity and somewhat earlier for XII and RLN activities; RLN HFO activity spanned most of the TI period. These data suggest that fast oscillatory rhythms in respiratory‐related motor discharges underlie only the I phase. Supported by NS049310.