The Journal of Bone and Joint Surgery 81:191-199 (1999)
© 1999 The Journal of Bone and Joint Surgery, Inc.
The Effects of Melatonin Therapy on the Development of Scoliosis After Pinealectomy in the Chicken*
KEITH BAGNALL, PH.D. ,
V. JAMES RASO, M.SC. ,
MARC MOREAU, M.D.,
JAMES MAHOOD, M.D.,
XIAOPING WANG, M.D. and
JIE ZHAO, M.D., EDMONTON, ALBERTA, CANADA
Investigation performed at the Department of Cell Biology and Anatomy and the Department of Surgery, University of Alberta, Edmonton
The mechanism underlying the development of scoliosis after pinealectomy in young chickens is unknown. However, since the main product of the pineal gland is melatonin, melatonin remains an obvious focus in studies designed to discover this mechanism. One confounding factor is that serum melatonin levels are close to zero after pinealectomy but scoliosis does not develop in all chickens that have had this procedure. Therefore, the role of melatonin in the development of scoliosis in chickens after pinealectomy remains controversial.
In the current investigation, two pilot studies demonstrated that a physiological therapeutic dose of melatonin (2.5 milligrams per kilogram of body weight) restored the circadian rhythm of melatonin, as measured by serum assay. In the main study, this dose was administered daily starting either immediately after the pinealectomy or two weeks after it, when scoliosis had developed. Scoliosis was assessed on weekly radiographs, and the Cobb angle was determined for all chickens in which scoliosis developed.
Overall, scoliosis developed in only 56 percent (fifty) of the eighty-nine chickens that had had a pinealectomy; this rate was consistent throughout all experimental groups. Scoliosis did not develop in any of the control chickens, which did not have a pinealectomy. On the basis of the average Cobb angles in the chickens in which scoliosis had developed, it was determined that neither the prevalence nor the pattern of the scoliosis was affected by the therapy in any of the experimental groups.
It was thus concluded that melatonin therapy after pinealectomy in young chickens has no effect on the development or progression of scoliosis. These results raise doubts regarding the role of melatonin in the development of scoliosis after pinealectomy in the young chicken.
CLINICAL RELEVANCE: Although scoliosis has been produced in some animal studies, none of these models has proved to be entirely satisfactory. Consequently, research regarding adolescent idiopathic scoliosis has been hampered. Recently, it was shown that scoliosis with many characteristics similar to those seen in patients who have adolescent idiopathic scoliosis can be produced consistently in chickens after pinealectomy. This finding encourages the development of this model. An understanding of the mechanism involved in the development of scoliosis after pinealectomy in chickens might provide new insights into adolescent idiopathic scoliosis and aid in the development of novel treatment methods.
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