Influence of extracellular [K+] on inspiratory‐phase synchronization in arterially‐perfused adult rat

Abstract

Studies examining central respiratory control using reduced preparations commonly increase the K+ concentration ([K+]o) in the artificial cerebral spinal fluid (aCSF) supplied to the preparation in order to increase excitability and maintain stable respiratory output. Although studies have evaluated the influence of varying the [K+]o on temporal and spectral characteristics of inspiratory motor discharge in the in vitro transverse slice preparation, much less is know about the influence of [K+]o on these parameters in the arterially‐perfused adult rat preparation. Therefore, using this preparation, we examined the effects of perfusion with aCSF containing either 3 mM (n=9; low) or the typically used 6.25 mM (n=8; control) [K+]o on phrenic nerve discharge. During perfusion with low [K+]o, phrenic burst frequency was 16.6± 1.4 bpm, TI was 904±145 ms, and TE was 2.9±0.2 s; during perfusion with control [K+]o, phrenic burst frequency was 17.7± 1.7 bpm, TI was 741±47 ms, and TE was 2.9±0.3 s. Perfusion with low [K+]o also resulted in a broadening of the high frequency oscillation (HFO) spectral peak and HFO activity was dispersed across much of the inspiratory burst, with a shift in the onset of spectral activity to an earlier point in inspiration. These findings suggest that low [K+]o reduces inspiratory‐phase synchronization. Supported by NS045321 and NS049310