Memory-improving action of glucose: indirect evidence for a facilitation of hippocampal acetylcholine synthesis.

The effect of a 3 g/kg glucose injection on the velocity of the sodium-dependent high-affinity choline uptake mechanism in the hippocampus was both measured in quiet control mice and in mice immediately after training in an operant bar pressing task. Glucose did not significantly change high-affinity choline uptake in resting animals. High-affinity choline uptake in the hippocampus was increased by training in the operant bar pressing task. Glucose significantly reduced the amplitude of the increase in high-affinity choline uptake observed in the trained animals. Similarly, a 3 g/kg glucose injection also attenuated the increase in high-affinity choline uptake observed in animals injected with 1 mg/kg scopolamine. Finally, a 3 g/kg glucose injection significantly attenuated the amnesia produced by a post-training 1 mg/kg scopolamine injection in mice trained for an operant bar pressing task. These results provide additional evidence for an action of glucose on hippocampal cholinergic activity under conditions of high acetylcholine demand. This action may be mediated via an increase in acetyl coenzyme A availability, one of the precursors of acetylcholine. This facilitative effect of glucose on hippocampal acetylcholine synthesis may constitute the physiological basis for its facilitative action on memory and its attenuation of scopolamine amnesia.