Unusual dose-related effect of an endorphin analog in a complex maze

Abba J. Kastin, Michael D. Mauk, Andrew V. Schally, David H. Coy

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Hungry adult rats were tested in a 12-choice maze for their ability to find a reward of food 15 minutes after being injected peripherally with (D-Ala2)-β-endorphin. Injection of the endorphin analog in a dose of 80 μg/kg body weight resulted in rats running the maze significantly slower and with more errors than rats injected with diluent. Animals receiving a dose ten times larger (800 μg/kg) were indistinguishable from controls in both running speed and errors, thus making a toxic effect unlikely. Possible changes in appetite, thirst, olfaction, emotionality, and general motor activity did not seem to explain the results. The inverted U-shaped dose-related response seemed to represent a variant from previous observations with CNS-active peptides in that the smaller dose impaired rather than enhanced performance.

Original languageEnglish (US)
Pages (from-to)959-962
Number of pages4
JournalPhysiology AND Behavior
Issue number6
StatePublished - Jan 1 1980
Externally publishedYes


  • Activity
  • Behavior
  • CNS
  • Dose-response
  • Learning
  • Maze
  • Opiate
  • Peptide

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Behavioral Neuroscience


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