J Korean Pain Soc.  2002 Jun;15(1):26-31.

Expression of Inducible Heat Shock Protein 70 in the Rat's Spinal Cord after the Formalin Test

• Hwang JT
• Yoon TG
• Kim HJ
• Yum KW

Abstract

BACKGROUND: Heat shock proteins (HSPs) are induced in the central nervous system by stressful stimuli and are thought to assist in the maintenance of cellular integrity and viability. Recently, several lines of evidence have indicated that HSPs are related to the synaptic plasticity phenomenon. The purpose of this study was to investigate the hypothesis that HSPs can be expressed in the nervous system, which is related to the nociceptive stimuli induced by formalin injection into the rat's hind paw.
METHODS
Male Sprague-Dawley rats weighing 250 300 g were subcutaneously injected with 100micro of freshly made 5% formalin into the right hind paw. At 1 and 24 hour(s) after formalin injection, the right and left sides of the 5th and 6th lumbar spinal cord were collected. HSP90, HSP 70, and HSP27 levels were examined using Western blot analysis.
RESULTS
Pain related behaviors induced by formalin were typically observed during 1 hr after formalin injection. However, at 24 hr after formalin injection, such pain behaviors were rarely observed. Only at 1 hr after formalin injection, HSP70 was significantly more expressed in the ipsilateral and contralateral lumbar spinal cord (P < 0.05). The others did not show significant changes in HSPs levels compared to those of the control group.
CONCLUSIONS
These results suggest that the overexpression of HSP70 in the lumbar spinal cord at 1 hr after formalin injection, which is associated with painful stress, may be related to the molecular mechanism of central sensitization.

Keyword

Formalin test; Heat shock protein 70; Sensitization; Spinal cord

MeSH Terms

Blotting, Western
Central Nervous System
Central Nervous System Sensitization
Formaldehyde*
Heat-Shock Proteins*
Hot Temperature*
HSP70 Heat-Shock Proteins*
Humans
Male
Nervous System
Pain Measurement*
Plastics
Rats, Sprague-Dawley
Spinal Cord*
Formaldehyde
HSP70 Heat-Shock Proteins
Heat-Shock Proteins
Plastics