In a 2009 report, Sekiguchi et al. demonstrated that YKS treatment ameliorated aggressive behavior in mice administered with beta-amyloid protein [9]. They also demonstrated that YKS did not suppress motor activity, nor did it induce catalepsy. Takeda et al. reported that YKS attenuated abnormal glutamate release in rats receiving a diet deficient in zinc [10], and in another study, they reported that YKS significantly suppressed the increase in extracellular glutamate and aspartate in the hippocampus of zinc-deficient rats after KCl stimulation [11]. In 2008, Egashira et al. reported that YKS inhibited the 2,5-dimethoxy-4-iodoamphetamine-induced head-twitch response and decreased expression of 5-hydroxytryptamine 2A receptors in the prefrontal cortex [12]. Terawaki et al. reported a partial agonistic effect of YKS on human recombinant serotonin 1A receptors expressed in the membranes of Chinese hamster ovary cells [13]. These reports collectively suggest the involvement of serotonergic and glutamatergic functions in the underlying mechanism of YKS. Tabuchi et al. reported that YKS ameliorated cognitive disturbances in APP transgenic mice, which are an animal model of Alzheimer’s disease [14]. Shimada et al. in 2001 reported that an aqueous extract of the hooks and stems of Uncaria sinensis (Oliv.) Havil., Uncariae uncus cum ramulus, a herb included in YKS, protected against glutamate-induced neuronal death in cultured cerebellar granule cells [15]. They suggested that oxindole alkaloids, such as isorhynchophylline, isocorynoxeine, and rhynchophylline, and indole alkaloids, such as hirsuteine and hirsutine, were the active components in Uncaria [16]. These compounds may cause the clinical effects of YKS. Similarly, in 2012, Nishi et al. reported that at least some of the effects of YKS may be due to an alkaloid found in the hooks of Uncaria known as geissoschizine methyl ether (GM), which acted as a partial agonist at the 5-HT1A receptor [17]. This assessment was supported by their concurrent finding that treatment with GM reduced aggression and increased social behavior in socially isolated mice, while treatment with YKS lacking Uncaria hooks did not.