Restored cognitive function in rats with combined denervations in the temporal region: neurochemical aspects.

During early testing (1 week), there is a clear impairment of preference for novelty in rats with combined transections of the fiber connections between the temporal and lateral entorhinal cortices and the hippocampal perforant path (TC/LEC + PP lesions). During late testing (2-3 weeks), a complete recovery of the preference for novelty is seen. The purpose of this study was to pharmacologically examine whether cholinergic or glutamatergic systems might support the processes underlying the recovery. The cholinergic antagonist atropine sulfate caused a complete reappearance of the impaired preference for novelty in rats with TC/LEC + PP transections. The glutamatergic antagonist HA-966 only produced a moderate reactivation of the recovered lesion effect. A moderate impairment was also seen in intact rats treated with atropine or HA-966. The results suggest that blocking of cholinergic function impairs the recovered performance in this specific task without precluding the involvement of other uninvestigated neurochemical systems.