The effect of alpha-sialyl cholesterol (alpha-SC; alpha-D-N-acetylneuraminyl cholesterol) on disturbances of the central cholinergic system induced by ethylcholine mustard aziridinium ion (AF64A) and by scopolamine were studied by means of a step-down passive avoidance response and locomotor activities in mice. The levels of acetylcholine (ACh) in certain regions of the brain were measured to assess the neurochemical recovery promoted by alpha-SC. 2. Treatment with AF64A (2.5, 5 and 10 nmol, i.c.v.) impaired the 24 h retention latencies of animals in a dose-dependent manner, and scopolamine (0.5 mg kg-1, i.p.) also impaired the retention performance. Administration of alpha-SC (1 and 4 mg kg-1, p.o.) once daily for 13 days improved the retention performance in AF64A-treated animals in a dose-dependent manner, but not in the scopolamine-treated animals. 3. Treatment with AF64A (2.5, 5 and 10 nmol, i.c.v.) and scopolamine (0.5 mg kg-1, i.p.) increased vertical and horizontal locomotor activities. alpha-SC dose-dependently attenuated the increase in locomotor activities induced by 2.5 nmol of AF64A, but not the locomotor activities caused by 5 or 10 nmol of AF64A, or scopolamine (0.5 mg kg-1, i.p.). 4. The deficit retention performance of AF64A-treated animals was associated with depletion of ACh levels in the hippocampus, but not in the septum or cerebral cortex. Administration of alpha-SC to AF64A-treated animals dose-dependently reversed the depletion of ACh levels in the hippocampus. 5. The results indicate that alpha-SC had significant effects after oral administration of AF64A-treated animals. The behavioural recovery promoted by alpha-SC may be based on the reversal of ACh depletion in the hippocampus.
