Naloxone effects on schedule-controlled behavior in morphine-pelleted rats

Alice M. Young, Travis Thompson

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The effects of morphine pellet implantation and naloxone administration were examined in rats lever pressing under inter-response time schedules of food presentation. Subcutaneous implantation of a morphine pellet initially decreased lever-pressing rates. Tolerance to this effect developed within 3-4 days. Naloxone (0.25-1.0 mg/kg) decreased response rates in morphine-pelleted rats in a dose-dependent and time-dependent manner. All doses of naloxone severely decreased rates of lever pressing on days four to nine post-pellet. This rate-decreasing effect persisted 7-17 days for 0.25 mg/kg naloxone, 9-22 days for 0.50 mg/kg, and 13-28 days for 1.0 mg/kg. Decreases in response rate were due to an increased frequency of long pauses and not to marked shifts in the temporal patterning of those lever presses that did occur. Changes in response rate after naloxone were accompanied by body weight loss. Area values summarizing the naloxone-induced changes in response rate or body weight over time after pellet implantation increased as a function of naloxone dose. Naloxone (0.25-1.0 mg/kg) did not alter performance by placebo-pelleted rats.

Original languageEnglish
Pages (from-to)307-314
Number of pages8
Issue number3
StatePublished - Jan 1979


  • Morphine pellet
  • Naloxone
  • Precipitated abstinence
  • Rats
  • Schedule-controlled behaviors


Dive into the research topics of 'Naloxone effects on schedule-controlled behavior in morphine-pelleted rats'. Together they form a unique fingerprint.

Cite this