Yokukansan (Kampo medicinal formula) prevents the development of morphine tolerance by inhibiting the secretion of orexin A.

BACKGROUND: Yokukansan (YKS), a traditional herbal (Kampo) medicine consisting of seven herbs, is effective in the treatment of pain disorders, such as headache, postherpetic neuralgia, fibromyalgia, and trigeminal neuralgia, and we have previously shown it to be effective against morphine analgesic tolerance in rats. It has been reported that orexin receptor antagonists prevent the development of morphine tolerance and that YKS inhibits the secretion of orexin A in the hypothalamus. This study examined whether the inhibition of the secretion of orexin A by YKS is one mechanism underlying its effect against morphine analgesic tolerance. METHODS: Male Wistar rats were administered a subcutaneous injection of morphine hydrochloride (10 mg/kg/day) for 5 days. One group was preadministered YKS, starting 3 days before the morphine. The withdrawal latency following thermal stimulation was measured daily using a hot plate test. On day 5, the levels of orexin A in the plasma and the midbrain were measured, and the appearance of activated astrocytes in the midbrain was examined by immunofluorescence staining. RESULTS: The preadministration of YKS prevented the development of morphine tolerance. The repeated administration of morphine significantly increased the plasma and midbrain levels of orexin A and the activation of astrocytes. These increases were significantly inhibited by the preadministration of YKS. CONCLUSION: These results suggest that the preadministration of YKS attenuated the development of antinociceptive morphine tolerance and that the inhibition of orexin A secretion may be one mechanism underlying this phenomenon.

Inhibitory effect of the Kampo medicinal formula Yokukansan on acute stress-induced defecation in rats.

OBJECTIVES: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder with symptoms of abnormal defecation and abdominal discomfort. Psychological factors are well known to be involved in onset and exacerbation of IBS. A few studies have reported effectiveness of traditional herbal (Kampo) medicines in IBS treatment. Yokukansan (YKS) has been shown to have anti-stress and anxiolytic effects. We investigated the effect of YKS on defecation induced by stress and involvement of oxytocin (OT), a peptide hormone produced by the hypothalamus, in order to elucidate the mechanism of YKS action. METHODS AND RESULTS: Male Wistar rats were divided into four groups; control, YKS (300 mg/kg PO)-treated non-stress (YKS), acute stress (Stress), and YKS (300 mg/kg PO)-treated acute stress (Stress+YKS) groups. Rats in the Stress and Stress+YKS groups were exposed to a 15-min psychological stress procedure involving novel environmental stress. Levels of plasma OT in the YKS group were significantly higher compared with those in the Control group (P < 0.05), and OT levels in the Stress+YKS group were remarkably higher than those in the other groups (P < 0.01). Next, rats were divided into four groups; Stress, Stress+YKS, Atosiban (OT receptor antagonist; 1 mg/kg IP)-treated Stress+YKS (Stress+YKS+B), and OT (0.04 mg/kg IP)-treated acute stress (Stress+OT) groups. Rats were exposed to acute stress as in the previous experiment, and defecation during the stress load was measured. Administration of YKS or OT significantly inhibited defecation; however, administration of Atosiban partially abolished the inhibitory effect of YKS. Finally, direct action of YKS on motility of isolated colon was assessed. YKS (1 mg/mL, 5 mg/mL) did not inhibit spontaneous contraction. CONCLUSION: These results suggested that YKS influences stress-induced defecation and that increased OT secretion may be a mechanism underlying this phenomenon.

Antistress effects of Kampo medicine "Yokukansan" via regulation of orexin secretion.

OBJECTIVE: Various stressors induce stress responses through the hypothalamic-pituitary-adrenal and the sympathetic-adrenal-medullary axes, which are regulated, in part, by orexin. For example, secretion of orexin in the hypothalamus is increased in rats exposed to the stress of social isolation for 1 week. In this study, the antistress effects of Kampo medicine Yokukansan (YKS) via the regulation of orexin secretion were investigated using a rat model. METHODS AND RESULTS: The administration of 300 mg/kg per day of YKS to rats for 1 week significantly decreased the plasma orexin levels compared with non-treated rats, whereas the administration of 1,000 mg/kg of YKS had no effect on orexin levels. Therefore, 300 mg/kg of YKS was an effective dose for controlling orexin secretion. Subsequently, rats were divided into group-housed control (Con), individually housed stress (Stress), and individually housed YKS (300 mg/kg)-treated stress (Stress + YKS) groups. After 1 week, a resident-intruder aggression test was performed, and the plasma levels of orexin and corticosterone were measured. In the Stress group, aggressive behavior and the levels of corticosterone and orexin significantly increased compared with the Con group; however, these effects were inhibited in the Stress + YKS group. Further, an orexin receptor antagonist (TCS 1102; 10 mg/kg) was intraperitoneally administered to rats exposed to isolation stress to determine whether orexin was involved in stress responses. Under these conditions, aggressive behavior and the level of corticosterone significantly decreased compared with the Stress group. CONCLUSION: These results suggest that orexin is involved in the control of stress response and that YKS exerts an antistress effect via the regulation of orexin secretion.

Yokukansan, a Kampo medicine, prevents the development of morphine tolerance through the inhibition of spinal glial cell activation in rats.

BACKGROUND: Animal models have shown that glial cells (microglia and astrocytes) in the spinal cord undergo activation following peripheral injury associated with chronic pain, suggesting the involvement of these cells in pain diseases. We have previously reported that Yokukansan (YKS), a Japanese traditional herbal (Kampo) medicine, is effective against chronic pain through the suppression of spinal glial cell activation. Morphine is a widely-used opioid analgesic for relieving severe pain, but its repeated administration leads to the development of antinociceptive tolerance. The development of morphine tolerance is also reported to be caused by spinal glial cells activation. In the present study, we investigated the inhibitory effects of YKS on the development of morphine tolerance and the activation of the spinal microglia and astrocytes using a rat model. METHODS: Male Wistar rats received a subcutaneous injection of morphine hydrochloride (10 mg/kg/d) for 7 days, and the withdrawal latency to thermal stimulation was measured daily using a hot plate test. Thereafter, the appearance of activated microglia and astrocyte in the spinal cord (L5) was examined by immunofluorescence staining. Ionized calcium binding adapter molecule-1 (Iba-1) staining was used to label microglia and glial fibrillary acidic protein (GFAP) staining was performed to label astrocytes. YKS was administered mixed with powdered rodent chow at a concentration of 3%. RESULTS: The preadministration of YKS (started 3 d before the morphine injection) prevented the development of morphine tolerance. The repeated administration of morphine increased Iba-1 and GFAP immune reactivities in the spinal cord; however, these activations were inhibited by the preadministration of YKS. CONCLUSION: These results suggest that the preadministration of YKS attenuates the development of antinociceptive morphine tolerance, and the suppression of spinal glial cell activation may be one mechanism underlying this phenomenon.