Vitamin A Deficiency Impairs Learning Functions In Reversible Manner

November 7, 2000

Vitamin A Deficiency Impairs Learning Functions In Reversible Manner

November 7, 2000

La Jolla, CA – Removing Vitamin A from the diets of mice diminishes chemical changes in the brain considered the hallmarks of learning and memory. When vitamin A is added back to their diets, the impairment is reversed.

“These data indicate that vitamin A is necessary for optimal function in the hippocampus, which we know to be a main seat of learning,” said Salk researcher Sharoni Jacobs, who, with her colleagues, are presenting these results at the current Society for Neuroscience meeting in New Orleans, La.

Added Salk Professor 罗纳德·M·埃文斯, senior author of the study: “The study indicates that the detrimental effects of vitamin A deprivation are remarkably reversible, which offers hope to the millions of children worldwide with vitamin A-deficient diets.”

In the study, genetically identical litter mates were given either a normal diet or one lacking vitamin A. At periodic intervals, the hippocampus regions of their brains were examined for LTP (long-term potentiation) and LTD (long-term depression), chemical measures of brain cell adaptability long believed to correlate with learning ability.

“At 15 weeks of age, the responses of vitamin A-deprived mice are reduced to about 50 percent normal. At longer time points, LTP is stable at 50 percent, but LTD drops to almost undetectable levels,” said Jacobs.

Adding vitamin A back to the diet for as little as two days restores brain responses to normal levels.

Normal function was also restored when isolated hippocampus tissue from the mice was bathed in vitamin A, indicating that the nutrient functions in the hippocampus directly, not in other parts of the brain that might influence the important learning region.

The current work builds on earlier studies from Evans’ laboratory, in which researchers found that mice born without receptors for vitamin A in the hippocampus lacked LTP ability and performed under par in standardized learning tests. Receptors are molecules within brain cells that detect and respond to the vitamin.

“What couldn’t be ruled out in those studies, however, was that vitamin A activity was needed during embryonic development to establish normal learning functions,” said Evans. “Now we’ve shown that removing vitamin A from fully-developed animals impairs learning pathways, and equally important, the effects are reversible.”

Salk co-authors include Dinah Misner, Yasushi Shimizu, Luigi De Luca and Professor Charles Stevens. The study, titled “A required role for vitamin A signaling in hippocampal long-term synaptic plasticity,” was supported by the National Institutes of Health and the Howard Hughes Medical Institute (HHMI). Evans and Stevens are Howard Hughes Medical Institute investigators.

索尔克生物研究所（Salk Institute for Biological Studies）位于加利福尼亚州拉霍亚（La Jolla, Calif.），是一家独立的非营利机构，致力于生命科学的基础性发现，改善人类健康和生活条件，以及培养未来的研究人员。该研究所由乔纳斯·索尔克（Jonas Salk, M.D.）于1960年创立，得到了圣地亚哥市（City of San Diego）的土地赠予和“March of Dimes Birth Defects Foundation”的财政支持。.