LOCOMOTOR AND PASSIVE-AVOIDANCE DEFICITS FOLLOWING OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY

The characterization of sensory, motor and cognitive dysfunctions foll owing occlusion of the middle cerebral artery (MCA) is prerequisite to investigations of treatment intervention in animal models of ischemia . Different strategies are used to induce ischemia, but the focal, tra nsient occlusion of the MCA has been reported to result in neuropathol ogy most similar to that seen in clinical cerebral ischemia. If the MC A occlusion technique results in a stroke animal model, then the behav ioral impairments inherent in stroke should be manifested in this mode l. The present study provides a further characterization of behavioral alterations associated with MCA occlusion. Sprague-Dawley rats underw ent temporal occlusion of the right MCA, and at 1 mo and 2 mo postisch emia, were subsequently tested in passive avoidance behavior, motor co ordination, asymmetrical motor behavior, neurological functioning, noc turnal spontaneous and amphetamine-induced locomotor activity, and hal operidol-induced catalepsy. Results revealed that ischemic rats showed long-term impairments in sensory, motor and cognitive functions. The discrepancy with other studies reporting temporal MCA-induced behavior al deficits may be due to techniques used to induce ischemia and conse quent CNS damage, differences in time period of testing (i.e., immedia te vs. later postischemia, nighttime vs. daytime), number of test-rete sts over the course of the experiment, and age of the animals. The mec hanism involved in the MCA-induced behavioral changes may be represent ed by loss of dopamine receptors on striatal neurons. Histological ana lysis revealed damage limited to the lateral aspect of the striatum. T hese behavioral and anatomical data support MCA occlusion as a model o f ischemia, and elucidate important factors that should be controlled for in characterizing the MCA-induced neuropathological alterations.