Role of melatonin deficiency in the development of scoliosis in pinealectomised chickens

Abstract

We studied the possible role of melatonin deficiency in experimentally-induced scoliosis. A total of 90 chickens underwent pinealectomy on the third day after hatching: 30 were treated with serotonin, 30 with melatonin and 30 received no therapy (control group). Scoliosis developed in all the control group, in 22 of the serotonin group, and in only 6 of the melatonin group. The six melatonin-treated chickens with scoliosis had less severe spinal deformities than those in the serotonin-treated group. There were lower blood melatonin concentrations in chickens with scoliosis than in those without. Our findings suggest that melatonin deficiency contributes to the aetiology of this experimental scoliosis, probably by interfering with the normally symmetrical growth of the proprioceptive system involving the paraspinal muscles and the spine.

The effects of pineal gland transplantation on the production of spinal deformity and serum melatonin level following pinealectomy in the chicken

“…Recently, Bagnall et al [2] also reported that the production of a scoliotic curvature in young chickens was not affected by MLT administration after pinealectomy. These results are in sharp contrast to those reported by Machida et al [19,21], who designed a similar study and found that pineal gland transplantation and MLT therapy following pinealectomy procedure prevented the development of spinal deformity. The reason for the differences between these two studies is not obvious, and such a confusing disparity warrants additional study.…”

“…Conversely, the results show that scoliosis was observed in 58% and 50% of groups B and C, respectively. Although Machida et al [19,20,21,23] have reported that 100% of their pinealectomized chickens developed a scoliotic curve, these results have not been confirmed in other studies [1,2,3,9,14,30,33,34]. Recently, a 52% incidence of scoliosis after pinealectomy was reported by Wang et al [34], and this is confirmed by the results of our current study.…”

“…A review of the literature (Table 8) shows that, among the limited number of experimental studies of scoliotic deformity development following pinealectomy in chickens that have been published to our knowledge (including ours), all of them, except Machida et al [19,20,21,23] and Coillard and Rivard [9], demonstrated that scoliosis did not develop in all cases after pinealectomy in young chickens (2-3 days after hatching), even though serum MLT levels were significantly low [2,3,14,33,34]. Although there was no major difference in terms of definition of scoliosis, species of pinealectomized chicken or surgical pinealectomy technique among the studies, the observation period in these series ranged from 5 weeks to 32 weeks after pinealectomy, and the rate of experimentally induced scoliosis ranged from 52% to 100% [2,3,9,14,19,20,21,23,33,34]. The observation period was 12 weeks in the studies reported by Machida et al [19,20,21,23], but in those reported by Wang et al [33,34], Bagnall et al [2], and Beuerlein et al [3], it was only 5 weeks.…”

“…Although there was no major difference in terms of definition of scoliosis, species of pinealectomized chicken or surgical pinealectomy technique among the studies, the observation period in these series ranged from 5 weeks to 32 weeks after pinealectomy, and the rate of experimentally induced scoliosis ranged from 52% to 100% [2,3,9,14,19,20,21,23,33,34]. The observation period was 12 weeks in the studies reported by Machida et al [19,20,21,23], but in those reported by Wang et al [33,34], Bagnall et al [2], and Beuerlein et al [3], it was only 5 weeks. With the exception of the study by Kanemura et al [14], a 100% incidence of scoliotic deformity has been reported in all other studies that had an observation period of at least 12 weeks.…”

“…Furthermore, there is an age-dependent alteration of its circadian secretion during the human lifetime. Since the first experiment by Thillard [30] in new-born chickens, the observation that pinealectomy leads to an experimental scoliosis in chickens similar to that in humans has led to this procedure being adopted as an attractive model used extensively in experimental research [1,2,3,11,14,15,18,19,20,21,22,23,33,34]. However, the pathophysiological mechanism of the development of spinal deformity after experimental pinealectomy in young chickens has so far not been clearly explained.…”