Inactivity‐induced phrenic motor facilitation (iPMF) requires atypical PKCζ activity within phrenic motor neurons

Abstract

Reduced respiratory neural activity elicits a rebound increase in phrenic amplitude once respiratory neural activity is restored, a form of spinal plasticity termed inactivity‐induced phrenic motor facilitation (iPMF). We tested the hypothesis that the zeta isoform of atypical PKC (PKCζ) is necessary within phrenic motor neurons (PMNs) for iPMF. Rats received bilateral intrapleural injections of siRNA (Sieck et al., 2012; EB Abstract #1147.2) targeting PKCζ (30ul of 100pmol siRNA/side) once daily for 3 days to knock down PKCζ expression specifically within phrenic motor neurons. Control rats received a non‐targeting siRNA. The fourth day, rats were anesthetized and mechanically ventilated; the phrenic nerve was prepared for electrophysiological recordings. After baseline phrenic amplitude was established, respiratory neural activity was reversibly suppressed for 30min by hyperventilating until phrenic activity ceased. 60min following restoration of baseline conditions, rats treated with control injections expressed significant iPMF (82±19 %baseline, p<0.05), whereas iPMF was significantly attenuated (13±10 %baseline, p>;0.05) in siPKCζ treated rats. PKCζ knockdown was confirmed within ventral cervical spinal segments containing PMNs with western blot analysis (−31±3 %control; p<0.05). These data indicate that expression of PKCζ specifically within PMNs is necessary for iPMF. NIH105511