The Block Of Morphine-induced CPP Reinstatement By Dezocine And Relative Mechanism In Rats

The drug problem is a serious global public health challenge that we should collaboratively deal with.Running rampant of the drug not only result in serious public health problem,but also relate to various kinds violent crime and terrorism events.It cause damage to dividual or family,moreover obstruct national survival and our progress.According to the world drug report of the United Nations in 2015,cut-off 2013’s data,there are 246 million drug users worldwide,more than 27 million of them have developed into problem addicts,who need being intervened for drug addiction,abuse and psychological dependence.With the fast development of medical clinical and basic research,research of the mechanism of addiction goes deeply into the molecular level.The clinical treatment of physiological dependence has also made great achievements.Drug addiction and mental dependence have been defined as a chronic disease of protracted encephalopathy,which need madical treatment and social intervention timely.During the three stages of the addiction development cycle（Preoccupation/Anticipation（Craving）Stage,Withdrawal/Negative Affect Stage and Binge/Intoxication Stage）,both cause and accompany the variation of different neuroplasticity and neural adaptation.This results in a variety of physical and mental dependence symptoms,and these element are mutually reinforcing or interact as both cause and effect.But the effective and convenient treatments of reinstatement（Relapse）that base on mental dependence and compound kinds of cues of sociaty,psychology and environment are still insufficient,it is need more explore.The drug therapies what be used by current medicine are scruples due to addiction itself.Exploring an effective,high security and low addiction has been verified to psychological dependence and relapse,and have convenient access to and use of the drug as a new treatment of opiate addiction pharmaceutical solutions,there are the necessary practical significance.Dezocine came into the market at 1989 first.It is a chemical compound that the molecular structure similar to pentazocine and interactive with opioid receptors,which be used to deal with kinds of pain.But its adaptation was limited soon for controversy about pharmacological characteristic.Recently,Liu R etc.uncovered an explicit conclusion that dezocine is a kind of antagonist toκopioid receptor,and is a partial agonist toμ&δopioid receptor.Meanwhile,two novel molecular targets have been identified,they are transporters of NE and 5-HT.In vitro,dezocine disturb working of the transporters by means of concentration dependence,and inhibit reuptake of these two neurotransmitters,resulted in the corresponding neurotransmitters accumulated around the extracellular.In our study,we use modified Maldonado scale and the classical CPP model that research physiological addiction and psychological dependence as an criterion to evaluate therapeutic effect of dezocine.DARPP32 is target what adenylyl cyclase act on,It promotes phosphorylation of DARPP32 because Dopamine activate its receptor.The relative expression of p-DARPP32 reflect variation that dopamine receptor induced cell response intensity（uptake reward threshold value）,which influences directly the addictive and drug seeking behavior of the individual.We observe relative expression of p-DARPP32 in primary encephalic region of the brain reward system,including nucleus accumbens,ventral tegmental area,hippocampus and prefrontal cortex,try to make clear the possible underlying neural mechanism of dezocine for the treatment of morphine addiction and relapse.Dezocine alleviate the withdrawal syndrome of acute morphine addiction and block morphine-induced CPP reinstatement in rats.During the first 4 days of the acute withdrawal period,acute morphine withdrawal symptoms of therapeutic group by dezocine are milder than it of the group of natural morphine withdrawal.During the last 3 days of the acute withdrawal period,acute morphine withdrawal symptoms of therapeutic group by dezocine are in line with the group of therapeutic group by buprenorphine and natural withdrawal.In the whole the acute withdrawal period,the scoles of the therapeutic group by dezocine do not make a drastic change either.After the acute withdrawal period that lasting 7 days,naloxone-induced withdrawal syndrome of the therapeutic group by dezocine are lighter than it of other groups.For rats that CPP behavior has went extinct,ineffective dose morphine is incapable of lighting morphine-priming CPP of the therapeutic group by dezocine,there have a similar effect that compare with buprenorphine.In following experiments on animals,we design a set of dose ladder for U50488（a kind of specific KOR agonist）to disturb dezocine in its antagonistic effect ofκopioid receptor,and observe whether its treatment outcome would be weaken or not when its antagonistic effect ofκopioid receptor was reveral.Experimental results confirm that the appropriate dose of U50488 enable reverse therapeutic effect of dezocine in its blockage of CPP reinstatement.But there have no influence to dezocine therapeutic effect in using0.33mg/kg,1mg/kg and 3mg/kg U50388 dose.However partialμopioid receptor agonistic effect of dezocine what was retained show less influence in morphine-priming CPP reinstatement.Subsequently,naloxone is used in compatibility for rivaling partialμopioid receptor agonistic effect of dezocine,and then we observe possible aberrance that maybe exist in processing its therapeutic outcome of dezocine.The result show that the therapeutic effect of dezocine dose not be affected.According to these finding,we speculate that antagonistic effect ofκopioid receptor play a more important role than partial agonistic effect ofμopioid receptor in therapeutic outcome of dezocine,partial agonistic effect ofμopioid receptor is in a relatively minor position.In the last part of our study,by means of observing p-DARPP32 relative expression and its positive cells in main brain region of reward system,we found that it was markedly increased in all treated groups that their CPP reinstatement has been blocked by地佐辛,and the amount of its positive cells were increased significantly either.Nevertheless,these two indices did not change in the rats whoes CPP reinstatement has been stirred by low dose morphine-priming.Meanwhile,two indices possess same variation pattern.The result also shows that the data have no significant difference among those rats whose data of two indices has increased,in other words,enhanced dopamine-induced cellular responses exist in main four brain regions of the stem of reward system simultaneously.This responses characterized by dopamine“over flow”,result in elevating threshold of reward system that affects individual behavior ultimately.This is the main neuromechanism of dezocine for remedying morphine addiction.In this part of the study,we did not observe a corresponding increase in the rate-limiting enzyme（Dopa Decarboxylase,DDC）for dopamine synthesis,it is suggest that increased dopamine neurotransmitters are not provided through channels of enhanced biosynthesis but other channels.It is speculated thatκopioid receptors of neurons antagonism mediated changes in membrane Ca²⁺channels made the high concentration of extracellular fluid Ca²⁺into the cell,further induced the cytoplasmic dopamine vesicle exocytosis enhanced in the relevant brain region.This inference needs more research to confirm.Detection of norepinephrine and Serotonin in Rat CSF,for the first time,we confirmed that dezocine can also affect the levels of both neurotransmitters,norepinephrine and serotonin,in the central nervous system in vivo to increase their concentration in CSF.Presumably related to its in vitro can inhibit norepinephrine and serotonin transporter protein function,inhibition of their re-uptake.In summary,the results of this study show that dezocine can not only effectively relieve the acute withdrawal syndrome of morphine-addicted rats,but also can effectively block CPP reinstatement that was irritated by low dose morphine-priming.This phenomenon shows the application of the drug in the treatment of opiate withdrawal syndrome and the prevention and treatment of mental dependence.Its mechanism of action is mainly caused by itsκopioid receptors antagonistic effect,which induces the"over flow"of dopamine neurotransmitter in the brain circuit of the brain reward system,Its weakμreceptor partial agonistic effect is also involved in playing a relatively minor role.It is confirmed that dezocine can upregulate norepinephrine and serotonin concentrations in CSF in living animals.At present,dezocine as a perioperative analgesic drugs,widely used in clinical practice,its non-addictive and non-respiratory inhibition of the safety of the practice has been verified,is a non-controlled drugs.Compared to other controlled alternative medicine which used to treat opiate addiction,dezocine have better convenience of use and security.