Chronic reduction in dietary tryptophan leads to a selective impairment of contextual fear memory in mice.
The depletion of systemic tryptophan is an important tool to study the effects of reduced 5-HT on cognition. Indeed, previous reports indicated that acute depletion of TRP leads to a memory impairment in human subjects and rodents. From the view of nutrition, it is important to investigate the effects of chronic limitation of L-tryptophan (TRP) on learning and memory formation. In this study, we examined the effects of chronic consumption of a low TRP diet on memory formation in mice. Specifically, we assessed the ability to form contextual fear, cued fear, conditioned taste aversion, and spatial memories in mice fed a TRP-limited diet for at least 1 month. TRP-limited mice showed impaired formation of contextual fear memory that is hippocampus-dependent. In contrast, these mice showed normal hippocampus-dependent spatial memory in the Morris water maze test, as well as in cued fear and conditioned taste aversion memories, which are amygdala-dependent memory processes. Thus, dietary TRP restriction appears to result in selective impairments in hippocampus-dependent contextual fear memory formation in mice.
Uchida
Shusaku
S
Department of Agricultural Chemistry, Faculty of Agriculture, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
Umeeda
Hisahiro
H
Kitamoto
Aya
A
Masushige
Shoichi
S
Kida
Satoshi
S
D000818:Animals; D001921:Brain / Q000503:physiopathology*; D003214:Conditioning, Classical; D004032:Diet; D005239:Fear / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D014364:Tryptophan / Q000172:deficiency*
D014364:Tryptophan