Yonsei Med J.  2002 Jun;43(3):370-376. 10.3349/ymj.2002.43.3.370.

Effects of MK-801 and Morphine on Spinal C-Fos Expression during the Development of Neuropathic Pain

• Lee YW
• Park KA
• Lee WT

• KMID: 1105109
• DOI: http://doi.org/10.3349/ymj.2002.43.3.370

Abstract

The purpose of this study was to investigate the expression of c-fos in the spinal cord during the development of allodynia, induced by peripheral nerve injury. Following tight ligation of the left L5 and L6 spinal nerves of Sprague- Dawley rat, the lumbar spinal cord was postfixed following perfusion. Frontal frozen sections of 40nm were immunostained according to the peroxidase-antiperoxidase method. The allodynic threshold was checked with 8 calibrated von Frey filaments. MK-801 (0.3 mg/kg), morphine (3 mg/kg) and saline (as a placebo) were administered subcutaneously 30 min before, and 24 and 48 hrs after surgery. The tactile threshold decreased below 3 g since 2 days after surgery in the saline and morphine groups, but delayed a little in the MK-801 group. In the superficial layer the number of Fos-like immunoreactive neurones (Fos-LI) peaked at 2 hours and decreased thereafter, and reached normal levels 24 hrs following operation, for all groups. In the deep layer they were biphasic, - peaking at 2 and 24 hrs - in the saline group, but were suppressed in the morphine and MK-801 groups until 7 days following operation. The above discrepancy between the number of Fos-LI and the allodynic threshold showed that central sensitizations are not critically involved in the development of nerve injury induced tactile allodynia.

Keyword

Allodynia; central sensitization; spinal c-fos; MK-801; morphine

MeSH Terms

Analgesics, Opioid/*pharmacology
Animal
Dizocilpine Maleate/*pharmacology
Excitatory Amino Acid Antagonists/*pharmacology
Hyperesthesia/etiology/*metabolism
Ligation
Male
Morphine/*pharmacology
Proto-Oncogene Proteins c-fos/*metabolism
Rats
Rats, Sprague-Dawley
Spinal Cord/*metabolism
Spinal Nerves/injuries
Wounds and Injuries/complications