Abstract: High-affinity choline transport (HAChT) is the rate limiting step in the synthesis of acetylcholine (ACh). The activity of HAChT and the binding of its selective inhibitor, [3H]hemicholinium-3 (HC-3) are affected by a number of exogenous and endogenous factors. Previous experiments demonstrated that Vitamin E pretreatment could prevent the decrease in HAChT and the cognitive deficits induced by the cholinotoxin AF64A [38]. To further examine this effect these experiments determined whether Vitamin E would alter the efficacy of both irreversible (AF64A) and reversible (HC-3) inhibitors of HAChT. In Experiment 1, rats were pretreated with Vitamin E (50 mg/kg), 24 h and 15 min, prior to bilateral icv injection of AF64A (0, 0.75, 1.5, or 3.0 nmol). HAChT was assessed in hippocampal synaptosomes, 14 days following surgery. Vitamin E prevented the dose-dependent AF64A-induced inhibition of HAChT in the hippocampus (HPC). In a second experiment, rats were pretreated with Vitamin E as above, and infused (icv) with the reversible inhibitor of HAChT, HC-3 (20 μg), or CSF. HAChT in the HPC was assessed 30 min, 4, 12, or 24 h after injection. HC-3 produced a significant decrease of HAChT (58%) that was maximal at 4 h and recovered by 24 h. Vitamin E significantly attenuated, but did not prevent, the inhibition of HAChT produced by HC-3. These experiments demonstrate that Vitamin E pretreatment can attenuate the effects of both reversible and irreversible inhibitors of HAChT. These data are discussed in terms of potential underlying mechanisms. It is possible that the neuroprotectant effects of Vitamin E on both reversible and irreversible inhibitors of HAChT reflect an action at the choline carrier and not an antioxidant effect.
Keywords: Vitamin E, AF64A, Hemicholinium-3, Anti-oxidants, Choline uptake
