Contribution of norepinephrine to recovery of motor and cognitive function after damage to the rat cerebral cortex

Abstract

Research examining possible drug treatments to facilitate recovery from brain injury have typically examined either motor or cognitive deficits but not both. Although these studies have shown that the treatments are effective within the scope of the behavioral syndrome being investigated (i.e. motor or cognitive), there has been very little success in generalizing these drugs to the other domain. As the majority of traumatic brain injury cases in people involves both a cognitive and motor component, it is important to investigate the effects of accepted drug treatments for motor recovery on cognitive deficits, and vice versa. Many of the previous motor studies have examined the effects of drug treatments that facilitate NE activity in recovery of function following injury to the rat sensory motor cortex. However, the NE facilitating drugs have rarely been investigated as to possible effects, positive or negative, on recovery of cognitive impairments following brain injury. The present study examined the effects of NE facilitating agents on both a motor and cognitive injury in a series of three experiments. The two treatments chosen were amphetamine, which has been shown to facilitate recovery of motor function, but has not been investigated extensively in models of cognitive impairment; and reboxetine, a novel drug treatment in the restoration of function from either motor or cognitive deficits. In the current study, facilitation of motor recovery was successfully replicated with amphetamine. However, amphetamine treatment had no effect on recovery of cognitive impairments following brain injury. Reboxetine, a more selective drug for NE was not found to have an effect on either motor or cognitive impairments in the present series of experiments. Failure of reboxetine in the present study to significantly affect motor recovery, coupled with a replication of a strong amphetamine effect, indicates that additional neurotransmitter systems may be needed for recovery of motor function. While the neither reboxetine or amphetamine were found to be without effect on cognitive impairments, additional studies are needed to investigate the effects of accepted motor treatments on cognitive impairments.