The effects of melatonin therapy on the development of scoliosis after pinealectomy in the chicken

The mechanism underlying the development of scoliosis after pinealectomy in young chickens is unknown. However, since the main product of the pineal g land is melatonin, melatonin remains an obvious focus in studies designed t o discover this mechanism. One confounding factor is that serum melatonin l evels are close to zero after pinealectomy but scoliosis does not develop i n all chickens that have had this procedure. Therefore, the role of melaton in in the development of scoliosis in chickens after pinealectomy remains c ontroversial. In the current investigation, two pilot studies demonstrated that a physiol ogical therapeutic dose of melatonin (2.5 milligrams per kilogram of body w eight) restored the circadian rhythm of melatonin, as measured by serum ass ay. In the main study, this dose was administered daily starting either imm ediately after the pinealectomy or two weeks after it, when scoliosis had d eveloped, 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 a ll experimental groups. Scoliosis did not develop in any of the control chi ckens, 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 b y the therapy in any of the experimental groups. It was thus concluded that melatonin therapy after pinealectomy in young ch ickens 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 stu dies, none of these models has proved to be entirely satisfactory. Conseque ntly, 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 pro duced consistently in chickens after pinealectomy. This finding encourages the development of this model. An understanding of the mechanism involved i n the development of scoliosis after pinealectomy in chickens might provide new insights into adolescent idiopathic scoliosis and aid in the developme nt of novel treatment methods.