The usefulness of operant conditioning procedures to assess long-lasting deficits following transient focal ischemia in mice

In this study, we examined a number of short and long-term sensorimotor, behavioural and cognitive consequences of an experimental ischemia induced by a 60-min right middle cerebral artery occlusion (MCAO) in 129S2 mice. During 14 days after surgery, a classical sensorimotor assessment was conducted using hanging wire test, negative geotaxis test, grip strength test, accelerated rotarod test and locomotor activity-meter. In order to provide a technique for the assessment of more resistant consequences of ischemia on fine psychomotor control, the peak procedure (a modified version of the operant fixed-interval schedule of reinforcement) was used. This procedure also helped to objectify temporal perception in mice five weeks following surgery. On several sensorimotor tests, ischemic mice showed some degree of impairment which rapidly tended to improve after stroke, a profile of results substantially consistent with previous studies. Five weeks post-surgery, ischemic mice tested with the peak procedure exhibited a moderate but yet significant temporal regulation impairment along with a reduced response rate compared to control mice. The present results suggest that the peak procedure and other derived operant schedules of reinforcement may provide useful and sensitive tools for the long-term assessment of both behavioural and cognitive aspects of the consequences of an experimental ischemia.