Study On Pharmacological Activities Of Alpha-conopeptide Eb1.6and Synthesis Of Several Mutants Of Conoeptides

Objective: A variety of animal pain models were used to evaluate the analgesicactivity and side-effects of Eb1.6. In addition, several mutants of peptide Eb1.6andVt1.27were synthesized for the research on the structure-activity relationship.Methods:(1) Some models of chronic pain, such as partial sciatic nerve ligationmodel (PNL), chronic constriction injury of the sciatic nerve(CCI) or diabeticneuropathic pain model(DNP), were used to evaluate analgesic activities of Eb1.6.(2)Some models of acute pain models, such as acetic acid writhing, hot tail or hot platemethod, were used to determine the effect of Eb1.6on acute pain in mice.(3) Theacute-toxicity, morphine-like addiction and motor dysfunction of Eb1.6wereinvestigated using intravenous injection, naloxone abstinence and rotarod test,respectively.(4) Four Eb1.6mutants and seven Vt1.27mutants were synthesized byFmoc-solid phase synthesis and air oxidative folding.Results:(1) Eb1.6exhibited significant analgesic activities in PNL, CCI, DNP models. InPNL, the pain threshold elevation percentage of rats was (55.6±36.7)%4h afteradministration of24.9g/kg of Eb1.6(i.m.) and was significantly higher than the bestchronic analgesics (morphine5mg/Kg+gabapentin100mg/Kg)(23.5±19.3)%, thepotency were also found in intravenous injection. In CCI, the most analgesic activityappeared in2h after the administration of Eb1.6, and the analgesic activity remainedlonger time than the combination of morphine and gabapentin. In DNP, the mostanalgesic activity appeared in4h after the administration of Eb1.6(i.m. or i.v.), andwas significantly higher than the combination of morphine and gabapentin.(2) Eb1.6showed good analgesic activities in acute pain model. In mice aceticacid writhing, Eb1.6significantly reduced the number of mice writing in 166.3μg/kgdose. In hot tail and hot plate experiments, the analgesic activity of Eb1.6was significantly higher than positive control Vc1.1in the same dose (41.8μg/kg).(3) Eb1.6did not show significant side effects. In acute toxicity test, the mice didn’tshow obvious side-effects at the dose that five hundred times over the effective dose.166.3μg/kg (i.m.) of Eb1.6affect the motor function of mice. In addition, it didn’tshow morphine-like addictive symptom after the continuous administration of24.90μg/kg,249μg/kg,2490μg/kg of Eb1.6for8days.(4) Four Eb1.6mutants (Eb1.6[K11A], Eb1.6[L10A], Eb1.6[M9A], Eb1.6[M9R])and seven Vt1.27mutants (Vt1.27[H6A], Vt1.27[P9A], Vt1.27[D11A], Vt1.27[Y12A],Vt1.27[R14A], Vt1.27[F15A], Vt1.27[H6P、P9A]) were synthesized.Results:(1) alpha-conotoxin peptide Eb1.6can be administrated by intramuscular orintravenous. It showed strong analgesic activities in chronic pain models, and theanalgesic effect is lasting.(2) The analgesic effect of Eb1.6in acute pain models is lower than in chronicpain models, but it also showed good analgesic activities in acute pain models.(3) At the dose that ten or five hundred times higher than the effective dose,Eb1.6does not cause obvious toxicity, effects of morphine-like addictive or hinder themotor function i(4) Four mutants of peptide Eb1.6and seven mutants of peptide Vt1.27withdifferent physicochemical properties were synthesized by the replacement of someamino acids.