Preoperative regimens of magnesium facilitate recovery of function and prevent subcortical atrophy following lesions of the rat sensorimotor cortex

Following brain injury, there is a reduction of intra- and extracellular levels of magnesium (Mg⁺⁺), which may contribute to the severity of the lesion-induced behavioral impairments. Injections of magnesium prior to or after brain injury attenuate these behavioral impairments. The present study extends these findings by manipulating the number of injections and the time period between the injections and the time of injury. Rats were given either two or five daily preoperative injections of MgCl₂ (1 mmol/kg, ip), or saline (1 ml/kg, ip) with the final injection given 24 h prior to electrolytic lesions of the somatic sensorimotor cortex (SMC). Following SMC lesions the rats exhibited contralateral deficits in forelimb placing and locomotor placing. Rats treated with either two or five preoperative injections of MgCl₂ showed a reduction in the initial magnitude of the contralateral deficits and an accelerated rate of recovery compared to saline-treated rats. In addition, analysis of striatal atrophy revealed that MgCl₂ treatment prevented atrophy in the ipsilateral posterior striatum compared to rats treated with saline. These data suggest that preoperative injections of MgCl₂ produce facilitation of sensorimotor recovery and reduce subcortical atrophy. Moreover, to observe the beneficial effects of MgCl₂, the timing of injections need not be tied to the period immediately around the brain injury. The present data may indicate that daily supplements of magnesium may partially protect against some of the deleterious effects of brain injury.