Phrenic motoneuron structural plasticity across models of diaphragm muscle paralysis

Phrenic motoneuron morphology in rats was assessed quantitatively using confocal microscopy following unilateral diaphragm muscle paralysis induced by C2 spinal hemisection (SH) or tetrodotoxin phrenic nerve blockade (TTX). Ipsilateral motoneuron somal surface area decreased after SH and increased after TTX, indicating that structural plasticity does not depend on muscle inactivity. AbstractStructural plasticity in motoneurons may be influenced by activation history and motoneuron –muscle fiber interactions. The goal of this study was to examine the morphological adaptations of phrenic motoneurons following imposed motoneuron inactivity while controlling for diaphragm muscle inactivity. Well‐characterized rat models were used including unilateral C2 spinal hemisection (SH ; ipsilateral phrenic motoneurons and diaphragm muscle are inactive) and tetrodotoxin phrenic nerve blockade (TTX; ipsilateral diaphragm muscle is paralyzed while phrenic motoneuron activity is preserved). We hypothesized that inactivity of phrenic motoneurons would result in a decrease in motoneuro n size, consistent with a homeostatic increase in excitability. Phrenic motoneurons were retrogradely labeled by ipsilateral diaphragm muscle injection of fluorescent dextrans or cholera toxin subunit B. Following 2 weeks of diaphragm muscle paralysis, morphological parameters of labeled ipsilater al phrenic motoneurons were assessed quantitatively using fluorescence confocal microscopy. Compared to control...

Source: The Journal of Comparative Neurology - November 8, 2018 Category: Neurology Authors: Carlos B. Mantilla, Wen ‐Zhi Zhan, Heather M. Gransee, Y. S. Prakash, Gary C. Sieck Tags: RESEARCH ARTICLE Source Type: research