Ethnopharmacological relevance: Kamikihito (KKT) is a Kampo medicine that is prescribed in Japan for the treatment of anemia, insomnia and mental anxiety in Japan. However, its precise mechanism of action remains unclear.
Aim of the study: This study aimed to evaluate the possible antistress effect of KKT in rats with acute stress and the contribution of oxytocin to the process.
Materials and methods: Acute immobilization stress (AIS; for 90 min) was used to assess the effect of KKT on acute stress. Male Wistar rats were orally treated with KKT. Parameters of stress were evaluated, and concentrations of oxytocin in plasma and cerebrospinal fluid (CSF) were measured.
Results: AIS-induced defecation and fecal weight were significantly decreased because of treatment with KKT. The plasma levels of stress-related hormones following AIS were investigated. The pre-administration of KKT significantly increased adrenocorticotrophic hormone (ACTH) and corticosterone (CORT) levels following AIS. Conversely, there was no significant change in the plasma oxytocin level. Microdialysis and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) were used to monitor the oxytocin secretion in CSF. Oxytocin level increased during AIS following the treatment of KKT. At 30 min after AIS, the level remained higher than before AIS. Furthermore, using an open field test, the locomotion (exploratory behavior) immediately after AIS was examined. The total traveled distance decreased after AIS; however, the decrease was significantly inhibited by the treatment of KKT. However, the effect of KKT was obstructed by the pre-administration of the oxytocin receptor antagonist.
Conclusions: These results suggest that KKT has antistress activity and increased oxytocin secretion may be a mechanism underlying this phenomenon.
Keywords: Central nervous system; Kamikihito; Kampo medicine; Oxytocin; Stress.
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