Effects of daily spontaneous running on the electrophysiological properties of hindlimb motoneurones in rats

被引:74
作者
Beaumont, E [1 ]
Gardiner, P [1 ]
机构
[1] Univ Montreal, depkin, Montreal, PQ H3C 3J7, Canada
来源
JOURNAL OF PHYSIOLOGY-LONDON | 2002年 / 540卷 / 01期
关键词
D O I
10.1113/jphysiol.2001.013084
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
No evidence currently exists that motoneurone adaptations in electrophysiological properties can result from changes in the chronic level of neuromuscular activity. We examined, in anaesthetized (ketamine/xylazine) rats, the properties of motoneurones with axons in the tibial nerve, from rats performing daily spontaneous running exercise for 12 weeks in exercise wheels ('runners') and from rats confined to plastic cages ('controls'). Motoneurones innervating the hindlimb via the tibial nerve were impaled with sharp glass microelectrodes, and the properties of resting membrane potential, spike threshold, rheobase, input resistance, and the amplitude and time-course of the afterhyperpolarization (AHP) were measured. AHP half-decay time was used to separate motoneurones into 'fast' (AHP half-decay time < 20 ms) and 'slow' (AHP half-decay time greater than or equal to 20 ms), the proportions of which were not significantly different between controls (58% fast) and runners (65% fast). Two-way ANOVA and ANCOVA revealed differences between motoneurones of runners and controls which were confined to the 'slow' motoneurones. Specifically, runners had slow motoneurones with more negative resting membrane potentials and spike thresholds, larger rheobasic spike amplitudes, and larger amplitude AHPs compared to slow motoneurones of controls. These adaptations were not evident in comparing fast motoneurones from runners and controls. This is the first demonstration that physiological modifications in neuromuscular activity can influence basic motoneurone biophysical proper-ties. The results suggest that adaptations occur in the density, localization, and/or modulation of ionic membrane channels that control these properties. These changes might help offset the depolarization of spike threshold that occurs during rhythmic firing.
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页码:129 / 138
页数:10
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