Effect of Administering Freund's Complete Adjuvant to Spinal Nerves on the Development of Allodynia in the Rat

Park, Jong Yeon; Hwang, Jai Hyun

Abstract

BACKGROUND: Spinal nerve ligation injury causes a neuropathic pain syndrome that includes allodynia. Neuropathic pain is also induced by Freund's complete adjuvant (FCA)-induced inflammation. This study was designed to examine the development of mechanical and cold allodynia after FCA administration at the L4/L5 spinal nerves and to compare it with the effects of spinal nerve ligation at the same site.
METHODS
Rats were randomly allocated into three groups: (i) treatment with tight ligation of the left L5/L6 spinal nerves, (ii) wrapping of the L5/L6 spinal nerves with Spongostan(R) soaked in FCA, or (iii) wrapping of the L5/L6 spinal nerves with Spongostan(R) soaked in saline. Mechanical and cold allodynia were measured by applying von Frey filaments or acetone in both hind paws. To examine the development of allodynia, the frequencies of hind paw withdrawal to each type of stimulus were measured.
RESULTS
Both FCA administration and nerve ligation injury caused a marked mechanical and cold allodynia in the lesioned hind paw compared to saline treatment (P < 0.05). Furthermore, the frequencies of response of the lesioned hind paw to both types of stimulus were significantly greater than those on the contralateral side.
CONCLUSIONS
These results suggest that administration of FCA to the spinal nerves can produce a mechanical and cold allodynia with a similar profile of pain facilitation as nerve ligation.