Study On The Analgesic Activity Of αO-conotoxin GeXIVA[1,2] In Diabetic Neuropathic Pain And Safety Evaluation

Conotoxin(Conopeptides)are a group of active polypeptide secreted by the venom glands of Conus,a carnivorous mollusc that lives in tropical seas.It is generally composed of 12 to 46 amino acid residues and is rich in disulfide bonds.Their diversities in sequences,disulfide bonds,and modified amino acids make them different from peptide toxins and proteins secreted by terrestrial animals and can specifically act on various ion channels and neuronal and kinins receptors in cell membranes in animals.The characteristics of conotoxin including low molecular weight,various structures make them act on a wide range of targets rapidly and possess many specific functions.αO-conotoxins were the first sub-family found to act on nicotinic acetylcholine receptors(nAChRs).nAChRs are widely spread in the central and peripheral nervous system and have different genes encoding nAChR subunits,forming iso-pentyl ion channel complexes selective for cations,ranging from insects and fish to humans.It has been demonstrated that nAChRs are key targets for the screening,diagnosis,and treatment of a wide range of important diseases such as addiction,pain,cancer,mental retardation,Parkinson’s disease,psychosis,depression,myasthenia gravis,and other incurable diseases.Among them,α9α 10 nAChR is a new target for the treatment of neuralgia,cancer chemotherapy,breast cancer,lung cancer and wound healing.αO-conotoxins specifically and potently block α9α10 nAChR and are important for the development of basic neuroscience and potentially novel analgesic drugs.The purpose of this thesis is to study the safety and analgesic activity of the novel αO-conotoxin GeXIVA[1,2]discoverd in this laboratory which selectively blocks α9α10 nAChRin type I diabetes neuropathic pain model.A single dose of 100 mg/kg intraperitoneal injection of streptozotocin(STZ)was used to induce Type I diabetic neuropathic pain in rats.The analgesic efficacy of αO-conotoxin GeXIVA[1,2]was studied.The results showed that the αO-conotoxin GeXIVA[1,2]showed a very potent dose-dependent analgesic effect in the model of type 1 diabetes-induced neuropathic pain.It is significant that the analgesic activity of a single injection of GeXIVA[1,2]high dose(20 nmol and 50 nmol)remained for days 5,6 and 7 after drug withdrawal.In order to evaluate the safety of αO-conotoxin GeXIVA[1,2],Kunming species(KM)mice were used as test animals.In the treatment group,10 nmol of αO-conotoxin GeXIVA[1,2]were injected intramuscularly for 7 consecutive days.The control group was given an equal volume of saline.During the experiment,mice were monitored for body weight changes and observed for toxicity.24 hours after the end of the administration,the eye were removed on the 8th day to collect blood,and the blood routine and blood biochemical parameters of the mice were measured.At the same time,main organs were dissected and weighed.The toxicity of GeXIVA[1,2]was evaluated by recalculating the organ coefficient,and a preliminary evaluation of the dose safety of the drug was performed.The experimental results show that the αO-conotoxin GeXIVA[1,2]is safe in the dose range of this experiment,and has no obvious toxic or side effects.The αO-conotoxin GeXIVA[1,2]has good and long lasting analgesic activity.It has good safety within a certain dose range and is expected to be developed into an original new type of analgesic drug for clinical use.This study provides theoretical and experimental basis for the further research.