Denervation causes changes in electrophysiological properties in rat phrenic motoneurons.
Thirty-nine male adult rats were divided into a control group and a denervation group that had been subjected to phrenicotomy 4 weeks earlier. Electrophysiological membrane properties (input resistance and rheobase) of phrenic motoneurons were measured from intracellular recordings made with glass microelectrodes. Under anesthetized and artificially ventilated conditions, the recorded motoneurons were divided into recruited (spike discharge) and non-recruited (depolarization only) types. There was a significant inverse relationship between the rheobase and input resistance in the control rats, but not in the denervated rats. In the control rats, the mean value of rheobase in the non-recruited motoneurons was significantly higher than that in the recruited motoneurons. In denervated rats, however, the mean value of rheobase in the recruited motoneurons was identical to that in the non-recruited motoneurons. The results indicated that phrenicotomy induced a de-differentiation of electrophysiological properties of the phrenic motoneurons, and that these changes might be restricted to the motoneurons innervating fast-twitch, low fatigue resistance muscle fibers.
Miyata
H
H
Department of Biological Sciences, Faculty of Agriculture, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8515, Japan. hiro@po.cc.yamaguchi-u.ac.jp
Wada
N
N
D000818:Animals; D003714:Denervation; D003964:Diaphragm / Q000294:innervation; D017097:Electric Impedance; D004594:Electrophysiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008839:Microelectrodes; D009046:Motor Neurons / Q000502:physiology*; D010791:Phrenic Nerve / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar