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, i.p.), or saline (1 ml/kg, i.p.) 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.