Neuromodulatory effects of repetitive transcranial magnetic stimulation on neural plasticity and motor functions in rats with an incomplete spinal cord injury: A preliminary study

Abstract

We investigated the effects of intermittent theta-burst stimulation (iTBS) on locomotor function, motor plasticity, and axonal regeneration in an animal model of incomplete spinal cord injury (SCI). Aneurysm clips with different compression forces were applied extradurally around the spinal cord at T10. Motor plasticity was evaluated by examining the motor evoked potentials (MEPs). Long-term iTBS treatment was given at the post-SCI 5th week and continued for 2 weeks (5 consecutive days/week). Time-course changes in locomotor function and the axonal regeneration level were measured by the Basso Beattie Bresnahan (BBB) scale, and growth-associated protein (GAP)-43 expression was detected in brain and spinal cord tissues. iTBS-induced potentiation was reduced at post-1-week SCI lesion and had recovered by 4 weeks post-SCI lesion, except in the severe group. Multiple sessions of iTBS treatment enhanced the motor plasticity in all SCI rats. The locomotor function revealed no significant changes between pre- and post-iTBS treatment in SCI rats. The GAP-43 expression level in the spinal cord increased following 2 weeks of iTBS treatment compared to the sham-treatment group. This preclinical model may provide a translational platform to further investigate therapeutic mechanisms of transcranial magnetic stimulation and enhance the possibility of the potential use of TMS with the iTBS scheme for treating SCIs.

Motor Neuroplastic Effects of a Novel Paired Stimulation Technology in an Incomplete Spinal Cord Injury Animal Model

“…According to a prior study on healthy rats, MEP can be continually increased for up to 30 min following a single session of iTBS [ 37 ]. A study on an SCI animal model reported the effects of iTBS stimulation on mild and moderate SCI groups’ neuroplasticity, with enhanced MEPs from baseline after week 1 and week 4 stimulation compared to the severe SCI group [ 38 ], which is consistent with our current study results. In our current study, pre- vs. post-week 1 and week 4 also showed a significant increase in post_25 min ( p = 0.012 *) and post_30 min ( p = 0.026 *) MEPs ( Table 1 ).…”

“…Differentiating the effect of these stimulation waveforms is very difficult because the sham group also significantly improved its BBB score. In addition, another study previously mentioned that iTBS does not significantly improve BBB scores in mild or moderate SCI animal models [ 38 ].…”

“…The rats were checked daily and given postoperative care. The bladder of each rat was squeezed two times a day until spontaneous voiding occurred, and an intramuscular injection of ampicillin (100 mg/kg, subcutaneously (s.c.), Novopharm, Toronto, Canada) was given to prevent infection for five days [ 38 , 40 ] ( Figure 11 ).…”

“…To elicit hindlimb MEPs, the circular coil was set so that it was in slight contact with the scalp surface (locator coordinates AP: ±1.0 mm; ML: ±1.25 mm; bregma as the center) [ 42 ]. A detailed method was described in our previous publication [ 38 ]. In the SCI rat model, a single TMS pulse elicited MEPs to assess cortical excitability during each session.…”

Effects of Chronic High-Frequency rTMS Protocol on Respiratory Neuroplasticity Following C2 Spinal Cord Hemisection in Rats

“…This technique operates through its neuromodulatory effects on neuronal circuitry [23,24]. The potential of rTMS to improve outcomes following incomplete SCI has gained recognition in the past few years but has mainly been applied to enhance locomotor recovery [25][26][27] and sensorimotor restoration [27][28][29] in preclinical models of SCI.…”