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BEHAVIORAL PHARMACOLOGY
Agonist and µ Agonist/Antagonist Properties
Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York (J.L.M., J.M.B.); and Alcohol and Drug Abuse Research Center, McLean Hospital, Harvard Medical School, Belmont, Massachusetts (X.P., W.X., A.Z., S.S.N., J.L.N.)
Previous research has shown that compounds with mixed
and µ activity may have utility for the treatment of cocaine abuse and dependence. The present study characterizes the pharmacological profile of a bivalent morphinan that was shown to be a
opioid receptor agonist and a µ opioid receptor agonist/antagonist. MCL-145 [bis(N-cyclobutylmethylmorphinan) fumarate] is related to the morphinan cyclorphan and its N-cyclobutylmethyl derivative MCL-101 [3-hydroxy-N-cyclobutylmethyl morphinan S-(+)-mandelate]. MCL-145 consists of two morphinans connected by a spacer at the 3-hydroxy position. This compound had Ki values of 0.078 and 0.20 nM for the
and µ opioid receptors, respectively, using radioligand binding assays as shown by Neumeyer et al. in 2003. In the guanosine 5'-O -(3-[35 S]thiotriphosphate) binding assay, MCL-145 produced an Emax value of 80% for the
opioid receptor and 42% for the µ opioid receptor. The EC50 values obtained for this compound were 4.3 and 3.1 nM for the
and µ opioid receptors, respectively. In vivo MCL-145 produced a full dose-response curve in the 55°C warm water tail-flick test and was equipotent to morphine. The agonist properties of MCL-145 were antagonized by the µ-selective antagonist
-funaltrexamine and the
-selective antagonist nor-binaltorphimine. MCL-145 also acted as a µ antagonist, as measured by the inhibition of morphine-induced antinociception.
Address correspondence to: Dr. Jean M. Bidlack, Department of Pharmacology and Physiology, Box 711, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Rochester, NY 14642-8711. E-mail: jean_bidlack{at}urmc.rochester.edu
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Y.-J. Wang, Y.-M. Tao, F.-Y. Li, Y.-H. Wang, X.-J. Xu, J. Chen, Y.-L. Cao, Z.-Q. Chi, J. L. Neumeyer, A. Zhang, et al. Pharmacological Characterization of ATPM [(-)-3-Aminothiazolo[5,4-b]-N-cyclopropylmethylmorphinan hydrochloride], a Novel Mixed {kappa}-Agonist and {micro}-Agonist/-Antagonist That Attenuates Morphine Antinociceptive Tolerance and Heroin Self-Administration Behavior J. Pharmacol. Exp. Ther., April 1, 2009; 329(1): 306 - 313. [Abstract] [Full Text] [PDF] |
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