Beam-walking in rats: studies towards developing an animal model of functional recovery after brain injury

While it has long been recognized that humans recover function after stroke or head injury, the direct impact of drugs on recovery has only recently received attention. The ability of rats to traverse a narrow, elevated beam has proven to be particularly useful when studying the effects of pharmacologic manipulations on motor recovery following cortical injury. However, the effect of testing conditions on the recovery of beam-walking performance has not been investigated. Treatment with amphetamine facilitated recovery of beam-walking following cortical lesions regardless of whether 'massed' or 'spaced' trials were employed. Unexpectedly, the performance of sham-operated controls declined when tested with 'massed' trials. 'Prodding' sham-operated rats by tapping on the rump abolished this decline in performance, but resulted in enhanced recovery in lesioned animals. The results indicate that testing conditions can exert a significant influence on beam-walking performance and are important to consider when interpreting the impact of pharmacologic agents on the recovery process.