Traumatic brain injury enhances the amnesic effect of an NMDA antagonist in rats.
The authors have examined the effect of experimental traumatic brain injury on the amnesia produced by the N-methyl-D-aspartate (NMDA) antagonist MK-801. Rats were either subjected to a moderate level of fluid-percussion injury or prepared for injury but not injured ("sham injury"). Nine days following injury or sham injury, the rats were injected either with saline (sham/saline group, nine rats; injured/saline group, nine rats) or with 0.1 mg/kg of MK-801 (sham/MK-801 group, nine rats; injured/MK-801 group, eight rats) 30 minutes before being trained on a passive-avoidance task. Twenty-four hours later, the rats were tested for retention of the passive-avoidance task. Results revealed that the low dose of MK-801 did not significantly affect retention of the passive-avoidance task in the sham-injured group. In injured animals, administration of MK-801 produced a profound amnesia in contrast to the sham-injured animals treated with MK-801 and the injured animals treated with saline. To further investigate this enhanced sensitivity to the amnesic effects of MK-801 exhibited by the injured animals, nine injured and eight sham-injured rats were injected with 0.3 mg/kg of MK-801 15 minutes before injury. Results indicated that the animals treated with MK-801 before injury did not significantly differ from the sham-injured animals in retention of the passive-avoidance task. In addition, test results in the animals treated with MK-801 before injury and reinjected with MK-801 before passive-avoidance testing did not differ from those in untreated injured animals reinjected with saline before passive-avoidance testing. These findings indicate that MK-801 treatment before injury prevented the enhanced sensitivity to MK-801-induced amnesia that follows traumatic brain injury.
Hamm
R J
RJ
Department of Psychology, Virginia Commonwealth University/Medical College of Virginia, Richmond.
Pike
B R
BR
O'Dell
D M
DM
Lyeth
B G
BG
D000647:Amnesia / Q000139:chemically induced / Q000209:etiology*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D001924:Brain Concussion / Q000150:complications / Q000503:physiopathology; D001930:Brain Injuries / Q000150:complications* / Q000503:physiopathology; D016291:Dizocilpine Maleate / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors
D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate