Yu G, Li SH, Cui MX, Yan LD, Yong Z, Zhou PL, Su RB, Gong ZH. Multiple mechanisms underlying the long duration of action of thienorphine, a novel partial opioid agonist for the treatment of addiction.
CNS Neurosci Ther 2013;
20:282-8. [PMID:
24330593 DOI:
10.1111/cns.12210]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Revised: 10/28/2013] [Accepted: 10/30/2013] [Indexed: 12/01/2022] Open
Abstract
AIMS
It is considered that a long-acting therapy would be advantageous in the treatment of addiction. In a search for novel buprenorphine analogues, thienorphine was demonstrated to be an extremely long-acting orally active partial opioid agonist. This study explored the mechanisms underlying the long-lasting effects of thienorphine.
METHODS
The binding kinetics of [(3) H]thienorphine were measured in membrane preparations expressing cloned rat opioid receptors. Flow cytometric analysis was used to determine the effect of thienorphine on the surface opioid receptor number. The long-lasting effects of thienorphine were also confirmed at the tissue level and in vivo.
RESULTS
At 37°C, [(3) H]thienorphine showed rapid association with μ- and κ-opioid receptors, while its dissociation was sluggish and biphasic (K-1 = 0.21 min(-1) , K-2 = 0.0078 min(-1) for the μ-receptor; K-1 = 0.17 min(-1) , K-2 = 0.0042 min(-1) for the κ-receptor). Treatment with thienorphine for 24, 48, and 72 h downregulated surface μ-receptor in a dose- and time-dependent manner. The inhibitory effect of thienorphine on guinea pig ileum persisted for more than 120 min after prolonged washing. In vivo, thienorphine exhibited significant antagonism of morphine-induced antinociception for more than 7 days.
CONCLUSIONS
These results indicate that multiple factors, including persistent receptor occupation and enhanced receptor downregulation, may contribute to the long-lasting effects of thienorphine that would be beneficial for its application in addiction treatment.
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