Interaction of choline and scopolamine in human memory

In a previous study (1), 8 gm. of oral choline given in a single dose were found to partially reverse the amnestic and subjective effects of 0.43 mg of scopolamine. The present study determined whether similar effects could be produced by 14 gm of choline given in 4 divided doses over 24 hrs and whether choline's effects in either study were related to plasma choline concentration. Ten normal subjects were given memory tests on three separate days, once after receiving 14 gm choline and 0.35 mg scopolamine (Ch-Sc), once following placebo and scopolamine (Pl-Sc), and once following placebo and placebo (Pl-Pl). Scopolamine markedly impaired memory performance but there was no difference between the Ch-Sc and Pl-Sc conditions. Plasma choline levels were significantly elevated in the Ch-Sc condition of both the single dose and divided dose studies. There was no difference in levels between studies nor were differences in memory performance correlated with elevations in plasma choline. These results indicate that any enhancement of cholinergic activity due to increased dietary choline is transient and of small magnitude.