Synchrony is altered in the respiratory pattern generator following acute hypoxic challenge

Abstract

Arthur B. Otis stated in 1954 that the work of breathing accounts for a small fraction of basal metabolism and that inspiration, not expiration, consumes energy. In line with Otis’ findings, our hypothesis is that the respiratory control network uses synchrony, in addition to recruitment and firing rate changes, to generate an efficient respiratory pattern. We hypothesize that synchrony may have unique roles in respiration and that this property is malleable, adapting to maintain homeostasis. To test our hypotheses, we used the perfused in situ preparation of rat (SD/Harlan) and recorded (n=7) from the left phrenic nerve and ensembles of respiratory neurons (n=53) in the Bötzinger/pre‐Bötzinger region using a multielectrode array. Preparations were exposed to acute bouts (20–45s) of hypoxia and spike synchronization between neuronal pairs (n=240) was quantified during baseline and post‐hypoxic epochs (80s/epoch). Neuron pairs from populations which appeared homogenous with respect to firing pattern demonstrated consistent changes in coordinated firing after hypoxia with the exception of a subpopulation of expiratory neurons which showed both increasing and decreasing synchrony. We conclude that synchronization is malleable within populations of the respiratory pattern generator and may contribute to patterning changes during post hypoxic frequency decline. Funded by AHA SDG 0735037N and NIH HL090554