Serotonergic and dopaminergic systems are implicated in antidepressant-like effects of chotosan , a Kampo formula, in mice

Ameliorating effect of chotosan and its active component, Uncaria hook, on lipopolysaccharide-induced anxiety-like behavior in mice

Introduction

In this study, we aimed to examine the effects of chotosan, a traditional Japanese botanical drug, and its active component, Uncaria hook, on anxiety-like behaviors induced by systemic inflammation in mice.

Methods

To induce systemic inflammation, the mice were treated with lipopolysaccharide (LPS), a bacterial endotoxin. Prior to LPS treatment, the mice were administered chotosan or Uncaria hook orally each day for 14 days. Anxiety-like behavior of the mice was evaluated using the light-dark test 24 h after LPS treatment.

Results

Repeated administration of chotosan prevented anxiety-like behavior in both normal and LPS-treated mice. Similarly, administration of Uncaria hook suppressed LPS-induced anxiety-like behavior in mice. Furthermore, treatment with tandospirone, a 5-HT1A receptor agonist, alleviated anxiety-like behavior in mice, whereas treatment with DOI, a 5-HT2A receptor agonist, enhanced anxiety-like behavior in mice. LPS treatment significantly increased serotonin (5-HT)2A receptor mRNA expression in the frontal cortex, whereas 5-HT1A receptor mRNA expression remained unchanged in the hippocampus. Notably, chotosan significantly suppressed the mRNA expression of 5-HT2A receptor.

Discussion

These findings indicate that chotosan exerts anxiolytic-like effects in the context of inflammation-induced anxiety, potentially mediated by the inhibition of 5-HT2A receptor hyperfunction in LPS-treated mice. Consequently, we postulate that chotosan may be effective in managing inflammation-induced anxiety-like behaviors.

Ninjinyoeito Prevents Onset of Depression-Like Behavior and Reduces Hippocampal iNOS Expression in Senescence-Accelerated Mouse Prone 8 Mice

Late-life depression is a globally prevalent disorder. Ninjinyoeito (NYT), a traditional Japanese herbal medicine, attenuates depressive symptoms in older patients. However, the mechanisms underlying the antidepressive effect of NYT are unknown. In this study, we investigated the mechanism of the action of NYT using senescence-accelerated mouse prone 8 (SAMP8) mice, which exhibit accelerated aging. SAMP8 mice were treated with NYT starting at 12 weeks of age. Twelve-week-old SAMP8 mice did not show prolonged immobility time in the tail suspension test compared with age-matched SAMR1 mice (normal aging control). At 34 weeks of age, vehicle-treated SAMP8 mice displayed prolonged immobility time compared with SAMR1 mice. NYT-treated SAMP8 mice showed a shorter immobility time than that of vehicle-treated SAMP8 mice. Notably, NYT decreased hippocampal inducible nitric oxide synthase (iNOS) expression in SAMP8 mice. There was no difference in iNOS expression between SAMR1 and vehicle-treated SAMP8 mice. Subchronic (5 days) administration of an iNOS inhibitor, 1400 W, shortened the immobility time in SAMP8 mice. These results suggest that NYT prevents an increase in immobility time of SAMP8 mice by decreasing iNOS levels in the hippocampus. Therefore, the antidepressive effect of NYT in older patients might be mediated, at least in part, by the downregulation of iNOS in the brain. Our data suggest that NYT is useful to prevent the onset of depression with aging.