J Korean Pain Soc.  2001 Jun;14(1):7-11.

Effects of Bupivacaine Pretreatment at the Periphery on the Expression of Mechanical Hyperalgesia in a Rat Model of Peripheral Neuropathy

• Chung YB
• Leem JW
• Chung EJ
• Lee JC
• Choi Y

Abstract

BACKGROUND: Although several mechanisms of causalgia, which results from a partial injury to the peripheral nerve trunk, have been proposed, whether or not antidromic impulses from the injured neurons contribute to the development of the mechanical hyperalgesia has not been studied. The purpose of this experiment is was to investigate the role of antidromic impulses to the peripheral sensory receptor site on the development of mechanical hyperalgesia in a rat model of peripheral neuropathy.
METHODS
Rats were prepared with tight ligation of by tightly ligating the left fifth and sixth lumbar spinal nerves. The effect of bupivacaine pretreatment on the development of mechanical hyperalgesia was evaluated by injecting 0.5% bupivacaine (0.3 ml) into the plantar surface of the left hind paw before the skin incision was made. For the control group, normal saline (0.3 ml) was injected instead of bupivacaine. To measure the mechanical hyperalgesia, paw withdrawal thresholds were measured using a series of von Frey hairs. Mechanical hyperalgesia was measured a the day before, and 1, 2, 3, 4, 7, and 14 days after the surgery.
RESULTS
The control group showed decreased withdrawal thresholds from the day after the surgery (the values were 14.0+/-0.5, 8.9+/-1.3, 8.4+/-1.6, 6.9+/-1.2, 8.8+/-1.5, 10.5+/-1.3, and 8.6+/-1.3 g; at 1, 1, 2, 3, 4, 7, and 14 days after the surgery, respectively). However, withdrawal thresholds of the bupivacaine-pretreated group showed increased withdrawal thresholds for three days after the surgery (14.5+/-0.3, 12.6+/-1.4, 12.7+/-1.1, 10.5+/-1.3 g; at 1, 1, 2, 3 days after the surgery).
CONCLUSIONS
Our result suggests that antidromic impulses to the peripheral sensory receptors are at least partly responsible for the initial development of mechanical hyperalgesia in a rat model of peripheral neuropathy.

Keyword

Afferent sensory nerve; Antidromic impulses; Causalgia; Pain; Peripheral neuropathy; Receptor sensitization

MeSH Terms

Animals
Bupivacaine*
Causalgia
Hair
Hyperalgesia*
Ligation
Models, Animal*
Neurons
Peripheral Nerves
Peripheral Nervous System Diseases*
Rats*
Sensory Receptor Cells
Skin
Spinal Nerves
Bupivacaine