Psychopharmacology

, Volume 143, Issue 2, pp 190–196 | Cite as

Systemic effects of E-2078, a stabilized dynorphin A(1–8) analog, in rhesus monkeys

  • E. R. Butelman
  • Jeffrey A. Vivian
  • J. Yu
  • Mary-Jeanne Kreek
  • James H. Woods
ORIGINAL INVESTIGATION

Abstract

Rationale: E-2078 ([N-methyl-Tyr1, N-methyl-Arg7, d-Leu8] dynorphin A(1–8) ethylamide) is a dynorphin A(1–8) analog with a reduced tendency to be biotransformed, when compared to the unmodified opioid peptide. E-2078 has been found to produce κ-opioid agonist effects in vivo in rodents. Objective: In the present studies, we investigated whether systemically administered E-2078 could produce κ-agonist effects in rhesus monkeys, in tests of antinociception, diuresis and ethylketocyclazocine (EKC) discrimination. Methods: E-2078 (0.32–18 mg/kg, SC, IM or IV) was tested in the warm water (50°, 55°C) tail withdrawal assay of thermal antinociception. The diuretic effects of E-2078 (0.056– 1.8 mg/kg, SC) were also compared to those of the κ-agonist, U69,593 (0.01–0.32 mg/kg, SC). Lastly, the effects of E-2078 (0.1–3.2 mg/kg, SC or IV) were studied in rhesus monkeys trained to discriminate EKC (0.0056 mg/kg SC) from vehicle, in a food-reinforced operant procedure. Results: E-2078 did not produce thermal antinociception in rhesus monkeys following SC or IM administration, up to the largest doses presently studied (i.e., 18 and 10 mg/kg, respectively). E-2078 caused thermal antinociception by the IV route, but this effect was not apparently mediated by κ- or µ-opioid receptors, as shown by its insensitivity to quadazocine (1 mg/kg) pretreatment. However, SC E-2078 caused diuresis, and this effect was blocked by quadazocine pretreatment, consistent with mediation by κ-opioid receptors. E-2078 generalized in EKC-discriminating monkeys, but only after the largest dose (3.2 mg/kg), and only following IV administration. Conclusions: The present studies suggest that systemically administered E-2078 can produce some κ-receptor mediated effects in rhesus monkeys, but its profile of action is not identical to non-peptidic κ-agonists following all routes of administration, or across all experimental situations.

Key words Antinociception Diuresis κ-Opioid receptors Macaca mulatta 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • E. R. Butelman
    • 1
  • Jeffrey A. Vivian
    • 2
  • J. Yu
    • 1
  • Mary-Jeanne Kreek
    • 1
  • James H. Woods
    • 2
  1. 1.Rockefeller University (Box 171), 1230 York Ave, New York, NY 10021, USA, e-mail: butelme@rockvax.rockefeller.edu, Fax: +1-212-327-8574US
  2. 2.Department of Pharmacology, University of Michigan, 1301 MSRB III, Ann Arbor, MI 48109, USAUS

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