Inhibition of betaarrestin mediated effects prolongs and potentiates opioid receptor-mediated analgesia

Abstract

The present invention provides a βarrestin knockout mouse useful for screening compounds for efficacy in controlling pain, methods of controlling pain in subjects by inhibiting binding of βarrestin to phosphorylated μ opioid receptors, and methods of screening a compound for activity in potentiating μ opioid receptor agonist activity (e.g., morphine activity) by determining whether or not said compound inhibits βarrestin binding to a phosphorylated μ opioid receptor.

That which is claimed is:  
     
         1 . A knockout mouse useful for testing the efficacy of potential analgesic agents, the cells of said mouse containing at least one inactive endogenous βarrestin-2 gene, said mouse exhibiting a phenotype of decreased sensitivity to pain after administration of a μ opioid receptor agonist as compared to the corresponding wild type mouse.  
     
     
         2 . A knockout mouse according to  claim 1 , wherein said mouse is heterozygous for an inactive endogenous βarrestin-2 gene.  
     
     
         3 . A knockout mouse according to  claim 1 , wherein said mouse is homozygous for an inactive endogenous βarrestin 2 gene.  
     
     
         4 . A method of controlling pain in a subject, comprising inhibiting βarrestin binding to the phosphorylated μ opioid receptors in said subject in an amount effective to induce or enhance analgesia in said subject.  
     
     
         5 . A method according to  claim 4 , further comprising the step of concurrently administering a μ opioid receptor agonist to said subject.  
     
     
         6 . A method according to  claim 5 , wherein said μ opioid receptor agonist is selected from the group consisting of morphine, codeine, oxycodeine, hydromorphone, diamorphine, methadone, fentanyl, sufentanil, buprenorphine, and meperidine.  
     
     
         7 . A method according to  claim 5 , wherein said μ opioid receptor agonist is morphine.  
     
     
         8 . A method of screening a compound for activity in controlling pain, comprising: 
 determining whether or not said compound inhibits βarrestin binding to a phosphorylated μ opioid receptor;    the inhibition of such binding by said compound indicating said compound may be active in controlling pain.    
     
     
         9 . A method according to  claim 8 , wherein said determining step is carried out in vitro.  
     
     
         10 . A method according to  claim 8 , wherein said βarrestin is βarrestin 2.  
     
     
         11 . A method of screening a compound for activity in potentiating μ opioid receptor agonist activity, comprising: 
 determining whether or not said compound inhibits βarrestin binding to a phosphorylated μ opioid receptor;  
 the inhibition of such binding by said compound indicating said compound is active in potentiating μ opioid receptor agonist activity.  
 
     
     
         12 . A method according to  claim 11 , wherein said determining step is carried out in vitro.  
     
     
         13 . A method according to  claim 11 , wherein said βarrestin is βarrestin 2.  
     
     
         14 . A method according to  claim 11 , wherein said μ opioid receptor agonist is selected from the group consisting of morphine, codeine, oxycodeine, hydromorphone, diamorphine, methadone, fentanyl, sufentanil, buprenorphine, meperidine.  
     
     
         15 . A method according to  claim 11 , wherein said μ opioid receptor agonist is morphine.