Post-weaning mice fed exclusively milk have deficits in induction of long-term depression in the CA1 hippocampal region and spatial learning and memory.
Previously, we have found that post-weaning mice fed exclusively milk display low-frequency exploratory behavior compared to mice fed a food pellet diet (Ishii et al., 2005a). Because cognitive functions play a key role in animal exploration, in the present study we examined the effect of an exclusively milk formula diet on spatial learning and memory in a water maze and also on induction of long-term potentiation (LTP) and long-term depression (LTD) at the Schaffer collateral-CA1 synapse in the hippocampus. Exclusively milk-fed mice exhibited slower learning and memory deficits in hidden water maze tests as compared with pellet-fed mice. Moreover, milk-fed mice showed a significant inhibition of LTD but a normal induction of LTP. Despite these functional deficits, adult neurogenesis in the dentate gyrus of the hippocampus, which has been proposed to have a causal relationship to spatial memory, was stimulated in milk-fed mice. These result suggest that an exclusively milk formula diet after weaning leads to a stimulation of hippocampal neurogenesis but causes deficits in the induction of LTD in the CA1 hippocampal region and impairment of spatial learning and memory.
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
Hideaki
H
Nishie
Ryouhei
R
Miyata
Ryu
R
Fujikawa
Ken-ichi
K
Kinoshita
Yoshikage
Y
Muroi
Toshiaki
T
Ishii
D000818:Animals; D056547:CA1 Region, Hippocampal; D004032:Diet / Q000009:adverse effects*; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D017774:Long-Term Potentiation; D036881:Long-Term Synaptic Depression; D008297:Male; D018782:Maze Learning; D008568:Memory; D051379:Mice; D008892:Milk / Q000009:adverse effects*; D055495:Neurogenesis / Q000502:physiology