Cholinergic involvement and synaptic dynamin 1 expression in Yokukansan-mediated improvement of spatial memory in a rat model of early Alzheimer's disease.

The aim of this study was to investigate the effect of Yokukansan (YKS) on the impairment of spatial memory and cholinergic involvement in a rat model of early-phase Alzheimer's disease (AD). In this model, rats underwent four-vessel transient cerebral ischemia and then were treated with beta amyloid oligomers injected intracerebroventricularly once daily for 7 days. These animals showed memory impairment in an eight-arm radial maze task without histological evidence of apoptosis but with a decrease in expression of hippocampal dynamin 1, an important factor in synaptic vesicle endocytosis. Oral administration of YKS for 2 weeks significantly increased the number of correct choices and decreased the number of error choices in the eight-arm radial maze task (P < 0.05). Moreover, YKS significantly increased high K⁺-evoked potentiation of acetylcholine (ACh) release (P < 0.05) and significantly increased the expression of dynamin 1 (P < 0.01) in the hippocampus. The ameliorative effect of YKS on spatial memory impairment in our rat model of early-phase AD may be mediated in part by an increase in ACh release and modulation of dynamin 1 expression, leading to improved synaptic function. Future studies will determine whether YKS is similarly useful in the treatment of memory defects in patients diagnosed with early-stage AD.

Yokukansan enhances pentobarbital-induced sleep in socially isolated mice: possible involvement of GABA(A)-benzodiazepine receptor complex.

In the present study, we investigated the effect of the Kampo medicine Yokukansan (YKS) on pentobarbital-induced sleep in group-housed and socially isolated mice. Socially isolated mice showed shorter sleeping time than the group-housed mice. YKS (300 mg/kg, p.o.) prolonged the pentobarbital-induced sleeping time in socially isolated mice without affecting pentobarbital sleep in group-housed mice. The prolongation of sleeping time by YKS was reversed by bicuculline (3 mg/kg, i.p.) and flumazenil (3 mg/kg, i.p.), but not WAY100635. These findings suggest that the GABA(A)-benzodiazepine receptor complex, but not 5-HT(1A) receptors, is involved in the reversal effect of YKS on the decrease of pentobarbital sleep by social isolation.

Yokukansan Enhances Pentobarbital-Induced Sleep in Socially Isolated Mice: Possible Involvement of GABA(A) - Benzodiazepine Receptor Complex.

In the present study, we investigated the effect of the Kampo medicine Yokukansan (YKS) on pentobarbital-induced sleep in group-housed and socially isolated mice. Socially isolated mice showed shorter sleeping time than the group-housed mice. YKS (300 mg/kg, p.o.) prolonged the pentobarbital-induced sleeping time in socially isolated mice without affecting pentobarbital sleep in group-housed mice. The prolongation of sleeping time by YKS was reversed by bicuculline (3 mg/kg, i.p.) and flumazenil (3 mg/kg, i.p.), but not WAY100635. These findings suggest that the GABA(A) - benzodiazepine receptor complex, but not 5-HT(1A) receptors, is involved in the reversal effect of YKS on the decrease of pentobarbital sleep by social isolation.

Effects of yokukansan on anxiety-like behavior in a rat model of cerebrovascular dementia.

Behavioral and psychological symptoms of dementia (BPSD) are commonly seen in patients with dementia. Current pharmacological approaches to treatment are inadequate, despite the availability of serotonergic agents to ameliorate anxiety, one of the symptoms of BPSD. The herbal medicine yokukansan has been demonstrated to improve BPSD in a randomized, single-blinded, placebo-controlled study. However, the mechanisms of the anxiolytic effect of yokukansan have not been clarified. There are also no reports on the anxiolytic effect of yokukansan in cerebrovascular ischemia models. In this study, we examined whether rats subjected to repeated cerebral ischemia exhibited anxiety-like behavior in a plus-maze task, a light/dark box test and an open-field task. We then investigated the effect of yokukansan on anxiety-like behavior in ischemic rats. Repeated ischemia was induced by the four-vessel occlusion method in which a 10-min ischemic episode was repeated once after 60 min. Yokukansan was orally administered once a day for 14 days from 7 days before ischemia induction. The last administration was performed 1 h before the behavioral experiments. The ischemic rats showed anxiety-like behavior in all three tasks, suggesting that this rat may be a good model for anxiety in cerebrovascular dementia. Yokukansan exhibited anxiolytic effects on the anxiety-like behavior in rats subjected to repeated cerebral ischemia, and exerted antagonistic effects on the wet-dog shakes induced by 1-(2,5-dimethoxy-4-indophenyl)-2-amino propane, a serotonin receptor (5-HT(2A)) agonist. This study revealed that yokukansan shows anxiolytic effects not only in normal animals but also in cerebrovascular model rats.

Yokukansan inhibits social isolation-induced aggression and methamphetamine-induced hyperlocomotion in rodents.

Behavioral and psychological symptoms of dementia (BPSD) are commonly seen in patients with Alzheimer's disease (AD) and other forms of senile dementia. BPSD have a serious impact on the quality of life of dementia patients, as well as on that of their caregivers. However, effective drug therapy for BPSD has not been established. Recently, the traditional Japanese medicine Yokukansan (YKS, Yi-gan san in Chinese) has been reported to improve BPSD, such as aggression, agitation, irritability, and hallucinations, in a randomized, single-blind, placebo-controlled study. However, the psychopharmacologic effects of YKS remain unexplored. In the present study, we investigated the effects of YKS on social isolation-induced aggressive behavior and methamphetamine- or MK-801-induced hyperlocomotion in rodents. Social isolation markedly induced aggressive behavior in male Wistar rats. Quetiapine at a dose of 10 mg/kg (per os (p.o.)) significantly inhibited this social isolation-induced aggressive behavior. YKS (100, 300 mg/kg, p.o.) also significantly inhibited the aggressive behavior. Moreover, risperidone (0.1 mg/kg, p.o.) significantly inhibited methamphetamine- or MK-801-induced hyperlocomotion in mice. YKS (300 mg/kg, p.o.) inhibited methamphetamine-induced hyperlocomotion, while YKS at the same dose had no effect on MK-801-induced hyperlocomotion. These findings suggest that YKS may be useful for the treatment of aggression and agitation, and that the psychopharmacologic effects of YKS might be mediated, in part, by inhibiting the activity of the dopaminergic system.