[Mechanical hyperalgesia induced by chronic morphine administration in young rats].

Abstract

OBJECTIVE:

To investigate the effects of chronic morphine administration on pain behaviors in young rats and to explore the mechanisms involved.

METHODS:

Sixteen SD young rats of 3-4 weeks were randomly divided into control and morphine administration groups. Young rats received saline (1 mL/kg) or morphine (10 mg/kg) subcutaneously. Each regimen was given once daily for 14 days. Pain behaviors were examined on day 1, 3, 5, 7, and 14 before the daily drug administration. Western blot was used to examine the expression of glutamate decarboxylase 65 (GAD65) in the spinal cord dorsal horn on day 14 after the last drug administration.

RESULTS:

Following 14 days of morphine administration, mechanical hyperalgesia was induced in young rats. Compared with control group, the mechanical withdrawal threshold of morphine group significantly decreased on days 3, 5,7 and 14. Chronic administration of morphine downregulated the expression of GAD65 in the spinal cord dorsal horn of young rats.

CONCLUSION:

Chronic morphine administration could induce mechanical hyperalgesia in young rats, and the downregulation of GAD65 in the spinal cord dorsal horn might play a critical role in the molecular mechanisms of morphine-induced hyperalgesia.

• Authors: Li Song, Bang-Xiang Yang, Yan Yin, Jun Li, Hui Liu
• Journal: Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition (Sichuan Da Xue Xue Bao Yi Xue Ban) Vol. 44 Issue 2 Pg. 209-12 (Mar 2013) ISSN: 1672-173X [Print] China
• PMID: 23745257 (Publication Type: Journal Article)

Chemical References

• Analgesics, Opioid
• Morphine
• Glutamate Decarboxylase
• glutamate decarboxylase 2

Topics

• Analgesics, Opioid (administration & dosage, adverse effects)
• Animals
• Down-Regulation
• Glutamate Decarboxylase (metabolism)
• Hyperalgesia (chemically induced)
• Male
• Morphine (administration & dosage, adverse effects)
• Posterior Horn Cells (enzymology)
• Rats
• Rats, Sprague-Dawley
• Spinal Cord (enzymology)
• Time Factors