Soleus motoneuron excitability after rat hindlimb unloading using histology and a new electrophysiological approach to record a neurographic analogue of the H-reflex

Region-Specific Responses of Adductor Longus Muscle to Gravitational Load-Dependent Activity in Wistar Hannover Rats

“…Such responses of EMG levels were also closely associated with the afferent neurogram [9], [10]. Further, it was reported that 14 days of hindlimb unloading caused a reduction of the threshold and maximal intensity of the neurographic analogue of the H-reflex induced by the soleus afferent excitation in rats [11]. According to the study of Desaphy et al [12], the responses of fiber size and myosin heavy chain (MHC) expression of rat soleus to unloading and reloading were closely associated with the reversible changes of resting sarcolemmal chloride conductance.…”

What Is Being Trained? How Divergent Forms of Plasticity Compete To Shape Locomotor Recovery after Spinal Cord Injury

“…90 The Hoffmann reflex (H-reflex) test of motorneuron pool excitability is a useful tool for assessing the modification of spinal plasticity, and the anti-gravity slow-twitch soleus muscle is well-recognized as an appropriate muscle for recording the modification of the H-reflex at the L5 ventral root level after HU. [91][92][93] It has been shown that the H-reflex has lowered thresholds after 3 weeks of HU and a similar observation correlates with reduced soma size in lumbar alphamotor neurons after 2 weeks of HU, suggesting changes in motorneuron excitability. 91,92 Treadmill training of intact rats that had previously undergone 2 weeks of HU showed robust alterations in neuromuscular pattern during locomotion and a broad disorganization of locomotor performance, including increased cycle duration, frequent hyperextensions of the ankle, and lateral instability.…”

“…[91][92][93] It has been shown that the H-reflex has lowered thresholds after 3 weeks of HU and a similar observation correlates with reduced soma size in lumbar alphamotor neurons after 2 weeks of HU, suggesting changes in motorneuron excitability. 91,92 Treadmill training of intact rats that had previously undergone 2 weeks of HU showed robust alterations in neuromuscular pattern during locomotion and a broad disorganization of locomotor performance, including increased cycle duration, frequent hyperextensions of the ankle, and lateral instability. 94 These rats also exhibited locomotor deficits similar to those seen previously by Lovely and colleagues in spinalized cats, 5 that is, paw drag at the start of swing phase and lack of hindlimb equilibrium, suggesting that HU, even in the intact animal, induced spinal cord changes that were influenced by both the lack of afferent information and altered supraspinal input.…”

“…87 HU greatly reduces muscle spindle afferent input, and this perturbation in afferent input has a robust effect on lumbar spinal circuitry. 88,89 Given that muscle spindle feedback has been shown to drive adaptive plasticity of propriospinal relay circuits and recovery after incomplete SCI, it could be hypothesized that HU would have a deleterious impact on recovery after SCI. 90 The Hoffmann reflex (H-reflex) test of motorneuron pool excitability is a useful tool for assessing the modification of spinal plasticity, and the anti-gravity slow-twitch soleus muscle is well-recognized as an appropriate muscle for recording the modification of the H-reflex at the L5 ventral root level after HU.…”