Body temperature response profiles for selective mu, de4lta and kappa opioid agonists in restrained and unrestrained rats

R. L. Spencer, V. J. Hruby, T. F. Burks

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


In many cases, body temperature is altered in response to opioid agonists, but the direction, magnitude and time course of alteration vary with a number of factors. Body temperature may be subject to differential modification by different opioid receptor types. The authors examined the effect (i.c.v.) of the selective mu, delta and kappa opioid agonists, [D-Ala2,MePhe4,Gly5-ol] enkephalin (DAGO), [D-Pen2,D-Pen5] enkephalin and U50488H, respectively, on the body temperature of restrained and unrestrained rats. Each of the three opioid agonists produced a differentiable profile of body temperature changes. DAGO caused a primary decrease in body temperature of restrained rats and an increase in body temperature of unrestrained rats. The pretreatment dose of naloxone necessary to attenuate the hyperthermic response to DAGO of unrestrained rats was 10 times higher than that required to block the hypothermic response to DAGO in restrained rats. Low doses of both [D-Pen2,D-Pen5]enkephalin and U50488H caused a decrease in body temperature of both restrained and unrestrained rats. Hypothermic responses to U50488H were not blocked by naloxone, whereas hypothermic responses to [D-Pen2-D-Pen5]enkephalin in unrestrained rats were potentiated by naloxone. The results indicate that the three compounds modified body temperature by different means, suggesting activation of different opioid, and perhaps nonopioid, receptors. This may reflect a differential modulation of body temperature by endogenous opioids depending on the specific peptide release and the receptor type activated. Besides the physiologic implications, body temperature responses provided a sensitive pharmacologic measure for distinguishing the in vivo activity of different selective opioid agonists.

Original languageEnglish (US)
Pages (from-to)92-101
Number of pages10
JournalJournal of Pharmacology and Experimental Therapeutics
Issue number1
StatePublished - 1988

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology


Dive into the research topics of 'Body temperature response profiles for selective mu, de4lta and kappa opioid agonists in restrained and unrestrained rats'. Together they form a unique fingerprint.

Cite this