Journal of Neuroscience, Vol 10, 3524-3530, Copyright © 1990 by Society for Neuroscience
Opiate antagonist nalmefene improves intracellular free Mg2+, bioenergetic state, and neurologic outcome following traumatic brain injury in rats
R Vink, TK McIntosh, R Rhomhanyi and AI Faden
Department of Chemistry and Biochemistry, James Cook University, Townsville, Australia.
Treatment of CNS trauma with the opiate antagonist naloxone improves
outcome, though the mechanisms of action remain speculative. Nalmefene is
another opiate-receptor antagonist, but it has substantially greater
potency and duration of action than naloxone. It also has increased
activity at kappa opiate receptors and has recently been shown to limit
histological changes and neurological dysfunction after traumatic spinal
cord injury. The present study examined the effects of treatment with
nalmefene on outcome after fluid-percussion-induced traumatic brain injury
in rats, using magnetic resonance spectroscopy to monitor acute metabolic
changes and behavioral tests to determine chronic neurological recovery.
Single-dose treatment with nalmefene (100 micrograms/kg, i.v.) at 30 min
after trauma significantly improved (p less than 0.05) neurological outcome
(up to 4 weeks) as compared to saline-treated controls. Early changes in
intracellular free-magnesium concentration, adenosine diphosphate
concentration, and cytosolic phosphorylation potential were all
significantly improved by nalmefene treatment, reflecting improved
bioenergetic state. We suggest that the ability of nalmefene to improve
cellular bioenergetics after trauma may in part account for the
neuroprotective effects of this and related compounds.