Antagonism of the discriminative effects of ethylketazocine, cyclazocine, and nalorphine in macaques

Alice M. Young, Kenneth R. Stephens

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

dl-Ethylketazocine (EKC, 0.01 mg/kg) and saline were established as discriminative stimuli for food-maintained responding in macaque monkeys. Thirty consecutive presses on a right or left lever were reinforced with food, contingent on whether EKC or saline were administered before the session. For tests of antagonism, naltrexone, or UM 979 [(l)-5,9-alpha-dimethyl-2-(3-furylmethyl)-2′-hydroxy-6,7-benzomorphan] was administered concomitantly with EKC, dl-cyclazocine, or nalorphine. Both antagonists blocked completely the EKC discriminative stimulus. The antagonism of the stimulus and rate-altering effects of EKC was surmountable, with considerable intersubject variability in the magnitude of the EKC dose increase required to overcome the blockade. Cyclazocine and nalophine, mixed agonist-antagonist opioids that share stimulus properties with EKC, were also susceptible to antagonism. Naltrexone antagonized completely the EKC stimulus effects of nalorphine; naltrexone and UM 979 antagonized completely the EKC stimulus effects of cyclazocine. Naltrexone antagonism of the cyclazocine stimulus was not surmountable, due to a lack of antagonism of the rate-decreasing effects of high cyclazocine doses.

Original languageEnglish
Pages (from-to)356-361
Number of pages6
JournalPsychopharmacology
Volume84
Issue number3
DOIs
StatePublished - Sep 1984

Keywords

  • Cyclazocine
  • Drug discrimination
  • Ethylketazocine
  • Macaque monkeys
  • Nalorphine
  • Naltrexone
  • κ{script} opioids

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