Korean J Anesthesiol.  2003 Feb;44(2):247-254. 10.4097/kjae.2003.44.2.247.

The Effects of Peripheral mu and kappa Opioid Receptor Agonists on the Thermal Injury Induced Hyperalgesia in the Rat

• Chun YS
• Jun JH
• Shim JC
• Kim KS
• Suh JK
• Yoo HK
• Seung IS

• KMID: 1936000
• DOI: http://doi.org/10.4097/kjae.2003.44.2.247

Abstract

BACKGROUND: Previous reports have described that the local administration of opioid receptor agonist can attenuate the nociceptive responses induced by a variety of inflammatory states. This study evaluated the effects of mu or kappa opioid receptor agonists peripherally administered at a site of injury on the state of thermal hyperalgesia induced by mild burn injury.
METHODS
Thermal injury was induced after briefly anesthetizing with halothane, by applying the left hindpaw to a hot plate (52.5 degree C) for 45 seconds. Paw withdrawal latency of the hindpaw was determined using an underglass thermal stimulus, which allowed the response latency of the injured paw to be obtained. In this work, the mu receptor agonist, morphine (10, 30, 100 microgram), or the kappa receptor agonist, U50,488H (10, 30, 100 microgram), was administered respectively at the injured site on the right hindpaw in rats. To compare the systemic effects of the drug, the same drug was administered at the normal left hindpaw site with mild burn injury. Naloxone (40 microgram/kg) was administered at the injured site or at the normal site to determine the reversibility of the opioid used.
RESULTS
Mild burn injury produced thermal hyperalgesia manifested as reduced paw withdrawal latency. Administration of either morphine (10, 30, 100 microgram) or U50,488H (10, 30, 100 microgram) at the injured site attenuated hyperalgesia in a dose-dependent manner. But the administration of drugs at the normal site had no effect on hyperalgesia at the injured site. In addition, naloxone had the effect of morphine and U50,488H reversed significantly.
CONCLUSIONS
These results suggest that peripheral mu or kappa opioid receptor administration at an injured site may play an important role in the hyperalgesia induced by mild burn injury.

Keyword

Burn injury; hyperalgesia; morphine; peripheral opioid receptor; U50,488H

MeSH Terms

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
Animals
Burns
Halothane
Hyperalgesia*
Morphine
Naloxone
Rats*
Reaction Time
Receptors, Opioid
Receptors, Opioid, kappa*
Receptors, Opioid, mu
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
Halothane
Morphine
Naloxone
Receptors, Opioid
Receptors, Opioid, kappa
Receptors, Opioid, mu