Three Aconitum Chinese Medicine Neurotoxicity In Vitro And In Vivo Experimental Studies

Aconitum medicine such as Radix Aconiti Lateralis Preparata, Radix Aconiti, Radix Aconiti kusnezoffii and its processed products are common clinical medication, with the effects of sedation, anti-inflammatory and analgesic, cardiotonic, anti-tumor. Moreover, these Chinese medicines are often used in reliving pain. In these medicine aconite alkaloid is the major pharmacological components, such as aconitine, mesaconitine, and hypaconitine, which show cardiac toxicity and can damage the peripheric spinal cord in clinical cases reports. However, there is no clear experimental data to prove it. Those reported studies using aconite alkaloid could not reflect the efficacy and toxic action of aconitine medicine. This research aimed to study the neurotoxicity of three kinds of representative aconitine medicine by using in vivo test and cultured embryo rat hippocampus neuron in vitro.In vitro study cultured hippocampal neurons" were treated with the extracts from three kinds of conitum medicine at various concentrations. Neuron survival was assessed by MTT method. Cell growth inhibition and 50% inhibition concentration (IC₅₀) were calculated. The result showed that with the increase of concentration of conitum medicine extract, inhibition ratio of neuron survival increased, indicating that these medicine exhibited significant toxicity to cultured neurons in vitro. The IC₅₀ of Radix Aconiti was 17.5mg/μl, Radix Aconiti Kusnezoffii 8.02 mg/μl and Radix Aconiti Lateralis Preparata 22.04 mg/μl. The rank of the toxicity to cultured hippocampal neurons was Radix Aconiti Kusnezoffii＞Radix Aconiti＞Radix Aconiti Lateralis Preparata.In vivo study three dosage groups and one control group for Radix Aconiti and Radix Aconiti Kusnezoffii were designed. Rats in each group were orally administrated with Radix Aconiti and Radix Aconiti kusnezoffii daily for consecutive 90 days. Cageside observation like mental state, behaviors, gland secretion, pupil changes was conducted. At the end of dosing period two third of the rats in each group were sacrificed to examine hematology, clinical chemistry, weight brain, organ coefficient and brain histopathology. The rest rats were sacrificed after another 4 weeks recovery period. The results showed that no behavior and mental abnormalites such as behavior activities, drowsiness, restless and eclampsia were found in treated group and control group. Piatelet counts of three dose groups of Radix Aconiti and Radix Aconiti Kusnezoffii were lower than those of control group; mean corpuscular-hemoglobin concentration of high dose- and low dose groups of Radix Aconiti was higher than that of control group; mean corpuscular volume of mid dose group of Radix Aconiti Kusnezoffii was lower than that of control group; mean corpuscular-hemoglobin of high dose group of Radix Aconiti was lower than that of control group. The differences between treated group and control group was statistically significant (P＜0.05), however, no dose-effect relation was found; moreover, the data changed within normal range. Therefore, these differences were not considered as treatment-related. Other hematology indexes in treated group showed no significant differences with control group.Aspartate amino transferase in mid- and low dose group, alanine aminotransferase in mid dose group, and total bilirubin in three dose group of Radix Aconiti were lower than those in control group. Aspartate amino transferase and alanine aminotransferase in low dose group, and total bilirubin in three dose groups of Radix Aconiti Kusnezoffii were statistically lower than those in control group. Although the differences mentioned above was statistical significance (P＜0.05), but no dose-effect relation was found, and the values fluctuated within normal range. In addition, creatinine and urea nitrogen in mid-, and low dose group of Radix Aconiti Kusnezoffii fluctuated in normal range. Other indexes in treated groups showed no statistical significance compared with control group. At the end of recovery period no behavior and mental abnormalities were found in the rats treated with test articles. Except for AST and TBIL which fluctuated within normal range, other indexes in treated groups like hematology, blood biochemistry, organ coefficient and brain histopathology showed no difference with the control. Therefore, no tardive neurotoxicity was found in the rats treated with test articles.This study showed that the three aconite medicine show no obvious neurotoxicity in vivo test, but it can inhibit neuron survival in vitro. These results imply that brain exposure level, blood-brain barrier and metabolism in vivo could be the main reasons for the different results in vivo and in vitro. Moreover, cultured hippocampal neuron is a useful model to study neurotoxicity in vitro.