| The opioid addiction is a state of physiologic or psychologic adaptation to opioid, characterized by behaviors that include one or more of the following: impaired control over opiate use, compulsive use, continued use despite harm, and craving. Two concepts contribute to opioid dependence: physical dependence, manifested by a withdrawal (abstinence) syndrome produced by abrupt cessation of opioid, and psychologic dependence, accompanied by feelings of satisfaction and a desire to repeat the drug experience or to avoid the discontent of not having it. However, the precise mechanisms underlying opiate addiction are not clearly understood, and little progress has been made in the treatment of the addictive disorders of opiate. Recent evidences suggested that several signal transduction pathways involved in opiate addiction, for example, AC-cAMP-PKA-CREB, NO-cGMP, Ca2+-CaM- CaMK-CREB signaling pathways, etc. The receptors, effectors and related proteins were phosphorylated by prolonged opioid agonists use,and several protein kinases, including protein kinase A( PKA), the protein kinase C( PKC), calmodulin- dependent kinaseâ…¡( CaMKâ…¡), G protein- coupled the receptor kinase( GRK) and mitogen- activated protein kinase(MAPK), involve in phosphorylation process. These kinases play an important role in the signal transduction of opioid receptors, tolerance and dependence of opiate.CCK is discovered initially in the gut as a gastrointestinal hormone with the function of contracting gallbladder and mediating pancreatic secretion, and subsequently localized in the central and peripheral nervous system as a neurotransmitter or neuromodulator. CCK is identified as several types of the peptide including 4, 8, 33, 39, and 58 amino acid forms. The sulfated carboxyl-terminal octapeptide (sCCK-8) is the biologically predominant...
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