Comparative Effects of Donepezil and Tacrine on Recall-Related Exploratory Behavior in a Subacute...

Background/Objectives: Neuroinflammation is increasingly recognized as an important contributor to Alzheimer-like cognitive impairment. Lipopolysaccharide (LPS) is commonly used in experimental models to trigger systemic immune activation and behavioral alterations associated with neuroinflammation. This study aimed to validate a subacute LPS-induced model of recall-phase impairment and to compare the effects of donepezil and tacrine on recall-related exploratory behavior in rats. Methods: Male Wistar rats were tested in a two-trial Y-maze paradigm consisting of an acquisition trial followed by a recall trial 24 h later. In the validation experiment, rats received saline or LPS 1 mg/kg intraperitoneally for four consecutive days. In the intervention experiment, rats received saline, LPS, or LPS combined with donepezil 1 or 3 mg/kg or tacrine 3 or 5 mg/kg. The primary recall-phase outcome was the unknown/known arm time ratio (U/K time ratio). Additional outcomes included arm times, arm entries, U/K entry ratios, discrimination indices, and mean time per entry. Results: Repeated LPS administration significantly reduced the U/K time ratio, decreased time- and entry-based discrimination indices, reduced time spent in the unknown arm, and decreased unknown-arm entries, without significantly altering acquisition-phase behavior, total entries, or mean time per entry. In the intervention experiment, donepezil 1 mg/kg and tacrine 5 mg/kg significantly increased the U/K time ratio compared with LPS. Discrimination indices and entry-based measures further supported a treatment-related shift toward novelty-directed exploration, while total arm entries and mean time per entry were not significantly changed. Conclusions: Subacute LPS administration produced a measurable recall-phase exploratory impairment in the Y-maze. Donepezil and tacrine attenuated several components of this impairment, with partially distinct dose-related behavioral profiles.