Yokukansan Inhibits the Development of Morphine Tolerance by Regulating Presynaptic Proteins in DRG Neurons.

Opioids, such as morphine, are used in clinical settings for the management of acute and chronic pain. However, long-term use of morphine leads to antinociceptive tolerance and hypersensitivity. The cellular and molecular mechanisms of morphine tolerance seem to be quite complex, with suggestions including internalization of the µ-opioid receptor (MOR), neuroinflammation with activation of microglia and astrocytes, and changes in synaptic function in the central nervous system. Yokukansan (YKS), a traditional Kampo medicine consisting of seven herbs, has been used to treat emotional instability, neurosis, and insomnia. Interestingly, recent studies have begun to reveal the inhibitory effect of YKS on the development of morphine tolerance. In the present study, we determined the effect of YKS on morphine tolerance formation and its mechanisms in a rat model, focusing on the synapses between primary sensory neurons and spinal dorsal horn secondary neurons. We found that morphine tolerance formation was significantly inhibited by YKS (0.3 or 1.0 g/kg/day) preadministration for 7 days. Repeated administration of morphine (10 mg/kg/day) increased the expression of presynaptic proteins, including synaptotagmin I, in the spinal cord, which was suppressed by YKS. Furthermore, these changes in presynaptic protein expression were more pronounced at isolectin B4 (IB4)-positive excitatory synapses around the lamina II of the dorsal horn. These results suggest that YKS suppresses the development of morphine tolerance by inhibiting the enhancement of presynaptic function of dorsal root ganglia neurons projecting to spinal dorsal horn neurons caused by continuous morphine administration.

In vitro and in vivo bioactivities of Ambrosia maritima and Bituminaria bituminosa organic extracts from Algeria.

INTRODUCTION: Two medicinal plants, Ambrosia maritima and Bituminaria bituminosa, growing in Algeria were investigated for their flavonoids content and their biological activities. METHODOLOGY: Different organic extracts were prepared from the aerial parts of each plant using maceration method followed by liquid/liquid type extractions. The anti-antioxidant activity was tested using the ß-carotene bleaching method. The anti-inflammatory activity was tested by performing the protein anti-denaturation assay. Acute toxicity and immunostimulatory effect were tested in mice, while the antimicrobial activity was tested according to the minimal inhibition concentration technique. RESULTS: In term of flavonoids content, ethyl acetate extract of B. bituminosa was the highest (193.39 ± 24.1 µg QE/mg). Ethyl acetate extract of A. maritima showed antioxidant activity with IC50 value of 11.72 ± 0.79 µg/mL. The hydroethanolic extract of A. maritima showed the best anti-denaturation effect in a dose-dependent manner with the IC50 value of 131.07 ± 0.027 µg/mL. The studied plants showed no toxicity or mortality in vivo. Both plants showed a significant immunostimulatory effect; while the Butanolic extract of B. bituminosa demonstrated the best antimicrobial activity against Staphylococcus aureus and Candida albicans strains. CONCLUSIONS: We recommend A. maritima and B. bituminosa as potent sources of antioxidants and as antimicrobial agents for further assays to better elucidate their actions on the immune system.

Kamikihito rescued depressive-like behaviors and hippocampus neurogenesis in chronic restraint stress rats.

Background and aim: Substantial evidence suggests the effectiveness of plant-based medicine in stress-related diseases. Kamikihito (KKT), a Japanese traditional herbal medicine (Kampo), has been used for anemia, insomnia, and anxiety. Recent studies revealed its ameliorating effect on cognitive and memory dysfunction in several animal models. We, therefore, determined whether daily supplementation of KKT has an antidepressant-like effect on the stress-induced behavioral and neurological changes in rats. Experimental procedure: The effect of KKT against the stress-induced changes in anxiety- and depressive-like behaviors and hippocampal neurogenesis were determined using a rat model of chronic restraint stress (CRS). KKT was orally administered daily at 300 or 1000 mg/kg during 21 consecutive days of CRS (6 h/day). The effect of CRS and KKT on physiological parameters, including body weight gain, food/water consumptions, plasma corticosterone (CORT) levels, and percentage of adrenal gland weight to body weight, were firstly measured. Anxiety- and depressive-like behaviors in rats were assessed in the open field test (OFT), sucrose preference test (SPT), and forced swimming test (FST). Hippocampal neurogenesis was determined by immunohistochemistry. Results and conclusion: CRS for 21 days caused a significant decrease in body weight gain and increase in plasma CORT levels and percentage of adrenal gland weight to body weight, which were rescued by KKT treatment. KKT also suppressed the CRS-induced anxiety- and depressive-like behaviors and impairment of hippocampal neurogenesis. These results suggest that daily treatment of KKT has a protective effect against physiological, neurological, and behavioral changes in a rat model of depression.

Analgesic effect of voluntary exercise in a rat model of persistent pain via suppression of microglial activation in the spinal cord.

In this study, we employed a rodent model for persistent allodynia and hyperalgesia to determine whether voluntary exercise could exert analgesic effects on these pain symptoms. Rats were subcutaneously injected with formalin into the plantar surface of the right hind paw to induce mechanical allodynia and hyperalgesia. We assessed the analgesic effects of a voluntary wheel running (VWR) using the von Frey test and investigated microglial proliferation in the dorsal horn of the spinal cord. We also determined the effect of formalin and VWR on the protein expression levels of brain-derived neurotrophic factor (BDNF), its receptor TrkB, and K+-Cl- cotransporter 2 (KCC2), which play a key role in inducing allodynia and hyperalgesia. Rats with access to the running wheels showed beneficial effects on persistent formalin-induced mechanical allodynia and hyperalgesia. The effects of VWR were elicited through the suppression of formalin-induced microglial proliferation, TrkB up-regulation, and KCC2 down-regulation in the spinal cord. BDNF, however, might not contribute to the beneficial effects of VWR. Our results show an analgesic effect of voluntary physical exercise in a rodent model with persistent pain, possibly through the regulation of microglial proliferation and TrkB and KCC2 expression in the spinal cord.