Antidepressant-like effect of chronic taurine administration and its hippocampal signal transduction in rats.

Taurine is one of the most abundant amino acids in the central nervous system, and it has various important functions as a neuromodulator and antioxidant. Taurine is expected to be involved in the mental disorders such as depression; however, knowledge of its function in relation to depression is limited. In this research, we tried to elucidate the effects of taurine supplementation on antidepressant-like behaviors in rats and depression-related signal transduction in the hippocampus. In behavioral tests, rats fed a high taurine (HT: 45 mmol/kg taurine) diet for 4 weeks (HT4w) showed decreased immobility in the forced swim test (FS) compared to controls. On the other hand, rats fed a low taurine (LT: 22.5 mmol/kg taurine) diet for 4 weeks or an HT diet for 2 weeks (HT2w) did not show a significant difference in FS compared to controls. In western blot analyses, the expression of glutamic acid decarboxylase (GAD) 65 and GAD67 in the hippocampus was not affected by taurine supplementation. However, the phosphorylation levels of extracellular signal-regulated kinase1/2 (ERK1/2), protein kinase B (Akt), glycogen synthase kinase3 beta (GSK3β), and cAMP response element-binding protein (CREB) were increased in the hippocampus of HT4w and HT2w rats. Phosphorylated calcium/calmodulin-dependent protein kinase II (CaMKII) was increased in the hippocampus of HT4w rats only. Moreover, no significant changes in these molecules were observed in the hippocampus of rats fed an HT diet for 1 day. In conclusion, our discoveries suggest that taurine supplementation has an antidepressant-like effect and an ability to change depression-related signaling cascades in the hippocampus.