ABSTRACT
Pain is one of the most prevalent health problems. Current medications for pain are mainly anticonvulsants， tricyclic antidepressants， and opioidergic drugs. However， their therapeutic effectiveness is limited during application， and some even have severe side effects. In recent years， research on natural ingredients from Chinese herbal medicine has been extensively conducted for their analgesic activities. A series of natural ingredients represented by alkaloids， coumarins， flavonoids， and terpenoids have shown great analgesic activity， and further studies on their analgesic mechanism have found that most natural products have multi-target analgesic mechanisms. It can exert analgesic effects by blocking ion channels， regulating related receptors， or inducing anti-inflammatory or antioxidant effects. In addition， many traditional Chinese medicine （TCM） formulas have shown great analgesic ability after clinical application and have multiple complex analgesic mechanisms. The drug cloud （dCloud） theory can better describe the mechanisms， and it can represent the complete therapeutic spectrum of multi-target analgesics from two dimensions， namely the "direct efficacy" that directly inhibits pain signals and the "background efficacy" that targets the root causes of pain. The authors summarized the research progress of natural ingredients with analgesic effects found in Chinese herbal medicine so far， as well as the analgesic efficacy and potential mechanisms of TCM formulas with great analgesic effects in clinical applications， so as to provide a new basis for searching for new analgesic drugs from TCM.
ABSTRACT
Aim To investigate the behavioral changes of the pain related neuromodulation and neurotransmission in peripheral and central nervous systems in rats with trigeminal neuralgia (TN)and provide a disease relevant animal model for mecha-nism study of TN.Methods The male SD rats were randomly divided into sham operation group and TN surgical group.The latter group was further divided into model group and gabapentin group (100 mg · kg-1 ). TN was induced by intravenous erythrosine B injection and laser irradiation.The pain behavior of rats was evaluated using mechanical pain threshold measured with Von Frey hairs.Fluorescence quantitative PCR technique was deployed to study the change of Tac1 mRNA expressions in trigeminal ganglia.Utilizing microdialysis technique followed by high performance liquid chromatography fluorescence detection (HPLC-FLD),the extracellular striatum fluid was collected and glutamate(Glu)concentration was determined.Results In the model group,the average mechanical pain threshold in facial ar-ea innervated by the trigeminal nerve remained below 4g after 7 days post surgery.The mechanical threshold of the model group (1.63 ±1.27)g was significantly lower (P<0.01)than the control group (24.17 ±4.49)g on day10 post surgery.In gen-eral,the mechanical withdraw threshold was decreased from the preoperative value of 26g to the postoperative value of (1.60 ± 1.74)g (P<0.01),and maintained stable at (0.71 ±1.24) g during the whole dynamic monitoring period from day7 to day60.The successful rate of this model was 63%.After sur-gery,Tac1 mRNA expression in trigeminal ganglia and extracel-lular Glu levels in striatum were significantly up-regulated (P<0.05 ) in the model group. Animals receiving Gabapentin showed significant improvement in pain symptoms,as well as re-ductions of Tac1 mRNA expression in trigeminal ganglia and ex-tracellular Glu concentration in striatum (P<0.05 ).Conclu-sions The above described photochemically induced TN rat model can partially mimic the clinical TN symptoms and its pathophysiology.Considering its overall high stability,it is very likely that this model could be used in preclinical mechanism study or drug screening of TN.