Effects of Morphine Dependency on Intervertebral Disc in the Rat

Background: A large proportion of patients presenting with lumbar disc disease are opium addicts in our region. It was, therefore, hypothesized that morphine might affect the intervertebral disc. We investigated the histological findings of morphine dependency on intervertebral discs in rat. Methods: Forty NMRI adult male rats (230-250 g) placed on ordinary diet and received aqueous solution of morphine. The solution contained 0.1mg/ml on the first day which gradually increased to 0.3 mg/ml during the first week, then continued at 0.4 mg/ml for four, seven and 11 weeks. Morphine dependency was confirmed by the presence of withdrawal syndromes using intraperitoneal naloxone at the end of each period. The H&E stained tissues were used to study the structure of disc and evaluation of degenerative changes. Results: Except for vascular proliferation of nucleus pulposus, an increase in the rate of matrix fibrillation, fibrosis, hyalinization, and dehiscence of nucleus pulposus was seen in morphine dependent rats compared with control group although it was not statistically significant possibly owing to relatively low sample size which limited the power to precisely reveal the difference. The duration of dependency did not affect the pathologic markers. Conclusion: The results of this study suggest that morphine dependency induces some pathologic changes in the intervertebral disc of the rat. Further investigation into degenerative markers with larger sample size is required. Iran J Med Sci 2006; 31(3): 147-150.