Spinal XXXX on the treadmill: changes in load pathways.

@entity1338 @entity468 @entity1566
Treadmill training and @entity1338 , an alpha-2 noradrenergic agonist, have been shown to improve locomotion after @entity1566 . We speculate that transmission in load pathways, which are involved in body support during stance, is specifically modified by training. This was evaluated by comparing two groups of spinal @entity468 ; one group (n = 11) was trained to walk until full-weight-bearing (3-4 weeks), and the other (shams; n = 7) was not. During an acute experiment, changes in group I pathways, monosynaptic excitation, disynaptic inhibition, and polysynaptic excitation were investigated by measuring the response amplitude in extensor motoneurons before and after @entity1338 injection. Monosynaptic excitation was not modified by @entity1338 but was decreased significantly by training. Disynaptic inhibition was significantly decreased by @entity1338 in both groups, but more significantly in trained @entity468 , and significantly reduced by training after @entity1338 . Also, @entity1338 could reverse group IB inhibition into polysynaptic excitation in both groups but more frequently in trained @entity468 . We also investigated whether fictive stepping revealed additional changes. In trained @entity468 , the phase-dependent modulation of all three responses was similar to patterns reported previously, but in shams, modulation of monosynaptic and polysynaptic responses was not. Overall, training appears to decrease monosynaptic excitation and enhance the effects of @entity1338 in the reduction of disynaptic inhibition and reversal to polysynaptic excitation. Because it is believed that polysynaptic excitatory group I pathways transmit locomotor drive to extensor motoneurons, we suggest that the latter changes would facilitate the recruitment of extensor muscles for recovering weight-bearing during stepping.
