AIMS: In this study, we investigated the effects of mitragynine on dopamine (DA) level and dopamine transporter (DAT) expression from the rat's frontal cortex.
METHODS: DA level was recorded in the brain samples of animals treated with acute or repeated exposure for 4 consecutive days with either vehicle or mitragynine (1 and 30 mg/kg) using electrochemical sensor. Animals were then decapitated and the brain regions were removed, snap-frozen in liquid nitrogen and immediately stored at -80 °C. DA level was quantified using Enzyme linked immunosorbent assay (ELISA) kits and DAT gene expression was determined using quantitative real time polymerase chain reaction (RT-qPCR).
RESULTS/OUTCOME: Mitragynine (1 and 30 mg/kg) did not increase DA release following acute treatment, however, after repeated exposure at day 4, mitragynine significantly and dose dependently increased DA release in the frontal cortex. In this study, we also observed a significant increase in DAT mRNA expression at day 4 in group treated with mitragynine (30 mg/kg).
CONCLUSION/INTERPRETATION: Data from this study indicates that mitragynine significantly increased DA release when administered repeatedly, increased in DAT mRNA expression with the highest tested dose (30 mg/kg). Therefore, the rewarding effects observed after mitragynine administration could be due to its ability to increase DA content in certain areas of the brain especially the frontal cortex.
MATERIALS AND METHODS: A total of 24 male rats were randomly divided into six groups: control, DM 1.5 month (DM1.5), DM 2 months (DM2) and the group with three different doses of CGA 12.5 (CGA1), 25 (CGA2), and 50 (CGA3) mg/KgBW. Frontal lobe tissue is taken for analysis of mRNA expression for NF-κB, MCP-1, IL-6, and GFAP using Reverse Transcriptase PCR (RT-PCR). Samples were also taken for histopathology preparation and stained by immunohistochemistry method using anti-GFAP antibodies to observe glial cell activation in frontal lobe tissue.
RESULTS: The group that was given CGA at all doses have statistically significant better memory function, i.e. DM2 versus CGA1 (p = 0.036), CGA2 (p = 0.040), and CGA3 (p = 0.021). The result of mRNA expression in NF-κB was lower in the group given CGA, i.e. DM2 compared to CGA2 (p = 0.007). mRNA expression of MCP-1 was significantly lower in all CGA treatment groups compared to the non-CGA group (p = 0.000). IL-6 mRNA expression was lower than the group not given CGA, DM compared to CGA2 (p = 0.028). GFAP mRNA expression was lower than the group given CGA in DM, DM2 group compared to CGA1 (p = 0.04) and CGA3 (p = 0.004).
CONCLUSION: Administration of CGA can improve memory function at all doses given, and can reduce brain inflammatory activity, especially in the CGA2 group.