Tokishakuyakusan ameliorates spatial memory deficits induced by ovariectomy combined with β-amyloid in rats.

Previously, we reported that ovariectomy (OVX) combined with β-amyloid peptide (Aβ) impaired spatial memory by decreasing extracellular acetylcholine (ACh) levels in the dorsal hippocampus. Here, we investigated the effect of tokishakuyakusan (TSS), a Kampo medicine, on the impairment of spatial memory induced by OVX combined with Aβ in rats. Repeated administration of TSS (300 mg/kg, p.o.) significantly decreased the number of errors in the eight-arm radial maze test. Though TSS had no effect on extracellular ACh levels at baseline, TSS significantly increased extracellular ACh levels in the dorsal hippocampus. These results suggest that TSS improves the impairment of spatial memory induced by OVX combined with Aβ by (at least in part) increasing extracellular ACh levels in the dorsal hippocampus.