LACK OF DELAYED-EFFECTS OF AMPHETAMINE, METHOXAMINE, AND PRAZOSIN (ADRENERGIC-DRUGS) ON BEHAVIORAL OUTCOME AFTER LATERAL FLUID PERCUSSION BRAIN INJURY IN THE RAT

This study examined the delayed effects of the administration of d-amp hetamine, methoxamine (an alpha 1-adrenergic receptor agonist), and pr azosin (an alpha 1-adrenergic receptor antagonist) on the behavioral o utcome of lateral fluid-percussion (FP) brain injury. Rats trained to perform a beam-walking task were subjected to brain injury of moderate severity (2.1 to 2.2 atm). Twenty-four hours after injury, rats were treated with amphetamine, methoxamine, or prazosin at two or three dif ferent dose levels. Amphetamine-treated animals displayed no significa nt improvement in beam-walking ability either during or after drug int oxication (from days 3 to 5 after brain injury). Similarly, neither me thoxamine nor prazosin significantly affected beam-walking ability dur ing or after drug intoxication. Neither amphetamine treatment at three different doses nor treatment with methoxamine or prazosin at two dif ferent doses affected the spatial learning disabilities of brain-injur ed animals. These results suggest that (1) unlike amphetamine administ ration after sensorimotor cortex (SMC) ablation or contusion brain inj ury models, amphetamine administration at 24 h after concussive FP bra in injury does not improve beam-walking performance; (2) unlike amphet amine administration 10 min after concussive FP brain injury amphetami ne administration 24 h after injury does not improve cognitive functio n; and (3) unlike prazosin administration after SMC ablation brain inj ury, prazosin administration 24 h after concussive FP brain injury doe s not effect beam-walking performance.