Inactivity-induced phrenic motor facilitation is associated with decreased phrenic burstto- burst variability

Abstract

Reduced respiratory neural activity in ventilated rats elicits rebound increases in phrenic discharge upon neural activity restoration, a plasticity called inactivity-induced phrenic motor facilitation (iPMF). We hypothesized that iPMF is associated with reduced phrenic burst-to-burst variability. Phrenic discharge was measured in Harlan (H) and Charles River (CR) Sprague-Dawley rats exposed to a neural apnea (NA), compared to time controls. Inspiratory (Ti) and expiratory time (Te) was assessed using Poincare plot analyses at baseline, 5 and 60 min post-apnea. In H+NA rats, standard deviations (SDl and SD2) for Ti and Te were significantly decreased at 5 and 60 min post�apnea (p< 0.01)when iPMF was expressed. while CR+NA rats experienced significant decreases in SD I and SD2 for Ti and Te at 5 (p<O.O 1). but not 60 min when iPMF was not expressed. These data suggest that iPMF is associated with decreased variability in Ti and Te.