CHAPTER 14:Beneficial Effects of Betaine on Water-Immersion Restraint Stress-Induced Memory Impairment in Mice

Betaine (glycine betaine) plays important roles as an osmolyte and a methyl donor in animals. While it has been reported to suppress the expression of proinflammatory molecules and reduce oxidative stress in aged rat kidneys and liver tissue, the effects on the central nervous system are not well known. In this study, we investigated the beneficial effects of betaine on water-immersion restraint stress (WIRS)-induced memory impairment and mRNA expressions. The repeated administration of betaine (0.163 mmol kg−1) prevented WIRS-induced delayed memory impairment. The subacute and acute administrations of betaine also prevented WIRS-induced memory impairment in the Y-maze test. The interleukin 1β (IL-1β) mRNA level was significantly increased at 2–3 h after WIRS, and the administration of betaine 1 h after WIRS blocked this increase in the frontal cortex. However, WIRS did not affect the levels of other inflammation- and oxidative stress-related mRNA expressions. Furthermore, although GABA transporter (GAT)-1, 2, and 3 mRNA expressions were significantly increased at 2 h after WIRS, betaine could not inhibit these increases. These data suggest that betaine has protective effects against WIRS-induced memory impairment, and the prevention of WIRS-induced changes in IL-1β mRNA expression may be one of the crucial factors in this ameliorating effect.