Korean J Anat.  2004 Aug;37(4):369-375.

Decrease in Zinc Concentration in the Rat Spinal Gray Matter Induced by Peripheral Nerve Ligation, and its Relations with Increased Pain Threshold

• Kim SJ
• Choi YH
• Yu YC
• Lee B
• Jo SM

Abstract

This study was designed to investigate any correlation between the mechanism of pain development and changes of histochemically-reactive zinc contents in the rat spinal cords following peripheal nerve ligation. Male Sprague-Dawley rats (270 ~290 g) were used for this study. We ligated a left-sided lumbar spinal nerve with silk under anesthesia using pentobarbital (50 mg/kg). Semmes-Weinstein monofilaments (Stoelting Company, Wood Dale, IL) was used to test for mechanical hyperalgesia. 30 micrometer-thick spinal cord cryosections were stained by automet-allography (Danscher, 1981). The density of zinc was significantly decreased in zinc concentration in the dorsal horn of 4th, 5th and 6th lumbar segments at 5 and 10 days after the spinal nerve ligation. Here, zinc depletion was apparent in superficial gray matter, especially layer III-IV. In addition the nerve ligated rats showed lower pain threshold. This increased pain sensation might be related with lowered vesicular zinc level in the superficial gray matter in the spinal cord. The present findings offer a proposed link between zinc and pain. Our interpretation is that there may be an extension of fine primary afferent fibers into lamina III and possibly lamina IV following peripheral nerve ligation. If further work bears out this conclusion, this would provide a possible explanation for the chronic pain states that sometimes follow peripheral nerve damage.

Keyword

Zinc; AMG; Pain model; Spinal gray matter; Spinal nerve ligation; Rat

MeSH Terms

Anesthesia
Animals
Chronic Pain
Horns
Humans
Hyperalgesia
Ligation*
Male
Pain Threshold*
Pentobarbital
Peripheral Nerves*
Rats*
Rats, Sprague-Dawley
Sensation
Silk
Spinal Cord
Spinal Nerves
Wood
Zinc*
Pentobarbital
Silk
Zinc