Thoracic 9 Spinal Transection-Induced Model of Muscle Spasticity in the Rat: A Systematic Electrophysiological and Histopathological Characterization

Abstract

The development of spinal hyper-reflexia as part of the spasticity syndrome represents one of the major complications associated with chronic spinal traumatic injury (SCI). The primary mechanism leading to progressive appearance of muscle spasticity is multimodal and may include loss of descending inhibitory tone, alteration of segmental interneuron-mediated inhibition and/or increased reflex activity to sensory input. Here, we characterized a chronic thoracic (Th 9) complete transection model of muscle spasticity in Sprague-Dawley (SD) rats. Isoflurane-anesthetized rats received a Th9 laminectomy and the spinal cord was transected using a scalpel blade. After the transection the presence of muscle spasticity quantified as stretch and cutaneous hyper-reflexia was identified and quantified as time-dependent changes in: i) ankle-rotation-evoked peripheral muscle resistance (PMR) and corresponding electromyography (EMG) activity, ii) Hoffmann reflex, and iii) EMG responses in gastrocnemius muscle after paw tactile stimulation for up to 8 months after injury. To validate the clinical relevance of this model, the treatment potency after systemic treatment with the clinically established anti-spastic agents baclofen (GABAB receptor agonist), tizanidine (α2-adrenergic agonist) and NGX424 (AMPA receptor antagonist) was also tested. During the first 3 months post spinal transection, a progressive increase in ankle rotation-evoked muscle resistance, Hoffmann reflex amplitude and increased EMG responses to peripherally applied tactile stimuli were consistently measured. These changes, indicative of the spasticity syndrome, then remained relatively stable for up to 8 months post injury. Systemic treatment with baclofen, tizanidine and NGX424 led to a significant but transient suppression of spinal hyper-reflexia. These data demonstrate that a chronic Th9 spinal transection model in adult SD rat represents a reliable experimental platform to be used in studying the pathophysiology of chronic spinal injury-induced spasticity. In addition a consistent anti-spastic effect measured after treatment with clinically effective anti-spastic agents indicate that this model can effectively be used in screening new anti-spasticity compounds or procedures aimed at modulating chronic spinal trauma-associated muscle spasticity.

Diverse spinal commissural neuron populations revealed by fate mapping and molecular profiling using a novel Robo3Cre mouse

“…Guinea pig polyclonal antibodies raised against GlyT2 (1:500, Synaptic Systems #272004), Tlx‐3 (1:10,000, Carmen Birchmeier [Storm et al, ], Max‐Delbrück‐Centrum for Molecular Medicine, Berlin), vesicular glutamate transporter (vGluT)‐1 (1:200, Millipore #AB5905), vGluT2 (1:200, Millipore #AB2251), and vGluT3 (1:500, Synaptic Systems #135204) were also used. The anti‐GlyT2 antibody was raised against a rat N‐terminus 229‐AA peptide and validated by western blot, reflecting a pattern and distribution consistent with previous spinal cord staining (Corleto et al, ). The anti‐Tlx‐3 antibody () was raised against a His‐tagged recombinant Tlx‐3 protein and exhibits a staining pattern in the spinal cord consistent with a Lacz reporter driven by Tlx‐3 Cre (Xu et al, ).…”

Neuropathic pain and spasticity: intricate consequences of spinal cord injury

“…18,66,67 Proposed mechanisms of both neuropathic pain and spasticity involve disinhibition from loss of descending pathways or interneurons, neuronal hyperexcitability, ectopic firing, sprouting, receptor upregulation, deafferentation effects on rostral or caudal neurons, glia activation and neuroinflammation, although the neuronal circuits involved in neuropathic pain and spasticity are likely to differ-at least to some extent. 60,67 The multidimensional nature of neuropathic pain and spasticity is important to consider when studying the underlying mechanisms or assessing treatment effects in both preclinical and clinical research, since the different symptoms and signs of neuropathic pain and spasticity can exist independently and do not necessarily have common underlying mechanisms or treatment responses. 18,29 Most clinical and preclinical research has focused on either pain or spasticity, while few studies have investigated both conditions at the same time.…”

Combination of epidural spinal cord stimulation and treadmill training with body weight support attenuates spasticity in adult rats with spinal cord transection

“…GAD65 is mainly found in membranes and nerve endings and may synthesize GABA for vesicular release [15]. GAD65 is known to decrease in rat models of SCI using spinal cord transection and may be related to the rhythmic inhibitory input to motoneurons during locomotion [16,17]. Therefore, upregulation of GAD65 is one of the possible mechanisms underlying the SCS-induced attenuation of spasticity.…”