Modulation of the biphasic pattern of cortical reorganization in spinal cord-transected rats by external magnetic...

A biphasic pattern of reorganization in the somatosensory cortical area, representing the hindlimb or forelimb, has been shown after complete spinal cord injury (cSCI) in rats. The present study hypothesized that extremely low-frequency magnetic fields (ELF-MF) would favourably modulate this biphasic pattern of cortical plasticity by altering brain-derived neurotrophic factor (BDNF) and neurite outgrowth inhibitor A (isoform of reticulon- 4) (Nogo-A) levels, leading to functional and electrophysiological recovery in cSCI rats. Adult male Wistar rats underwent cSCI at the T-13 spinal level, followed by ELF-MF exposure for either 5, 12, or 32 days, for analysis of the biphasic pattern. A set of motor and sensorimotor behavioural tests, spinal cord lesion volume, cortical electroencephalography (EEG), expression of neurotrophic factor (BDNF), and inhibitory molecule (Nogo-A) were recorded at each time period. Significant (p≤0.01) recovery was evident in the Basso-Beattie- Bresnahan (BBB) locomotor score, allodynia, grip strength, power spectrum of EEG waves, and lesion volume after 32 days of ELF-MF. Although both SCI and SCI+MF rats exhibited characteristic biphasic patterns in the expression of Nogo-A and BDNF, the SCI+MF group showed a significant increase in BDNF levels along with a decrease in Nogo-A. These findings suggest that ELF-MF enhances functional recovery after cSCI by moderating molecular and electrophysiological markers of cortical plasticity, without disrupting the inherent biphasic expression dynamics.