Effect of extracted Mitragyna speciosa korth subacute treatment on learning and memory in ovariectomized mice

A decrease in estrogen during menopause is associated with an impairment of learning and memory. This study aimed to investigate the effect of extracted Mitragyna speciosa Korth (MS) on learning and memory in ovariectomized mice. Female ICR mice were divided into 5 groups: SHAM (sham-operated), OVX (ovariectomy), ES (ovariectomy and injected with 0.04 mg/kg of 17 ß-estradiol for 21 days), MS10 (ovariectomy and treated with extracted MS containing 10 mg/kg of mitragynine for 21 days) and MS30 (ovariectomy and treated with extracted MS containing 30 mg/kg of mitragynine for 21 days). Novel object recognition test and Y-Maze test were used in order to determine the level of learning and memory. The density of choline acetyltransferase immunoreactivity (ChAT-ir) in the basal forebrain and parvalbumin immunoreactivity (PV-ir) in the prefrontal cortex and hippocampus were evaluated. The results demonstrated a significant decline in learning and memory in the OVX group compared to that of the SHAM (P<0.05). In contrast, learning and memory was improved in the ES and MS10 groups compared to that of the OVX. The density of ChAT-ir and PV-ir neurons was significantly reduced in the OVX and MS30 groups compared to that of the SHAM (P<0.05) but significantly increased in the ES and MS10 groups (P<0.05). Abnormal hematological test results were found in the ES and MS30 groups but not in the MS 10 group. Therefore, extracted MS containing 10 mg/kg of mitragynine subacute treatment may be effective and safer than the estrogen and extracted MS containing 30 mg/kg of mitragynine treatments.