Changes in melatonin receptors in relation to the development of scoliosis in pinealectomized chickens.
METHODS
The 2[125I]iodomelatonin binding assay was used to investigate the involvement of melatonin receptors in the development of scoliosis in pinealectomized chickens.


OBJECTIVE
To compare the binding properties of melatonin receptors in the thoracic spinal cord between pinealectomized chickens that had scoliosis develop and those that did not.


BACKGROUND
Surgical pinealectomy in young chickens induced scoliosis with a reported incidence of 50% to 100%. The factors regulating the development of scoliosis in this animal model are unclear. Melatonin receptors have been shown in the spinal cord of chickens, but their functions are still unknown. This study addresses the question as to whether spinal cord melatonin receptors are related to the pathogenesis of scoliosis in pinealectomized chickens.


METHODS
Control and pinealectomized chickens were kept under controlled lighting conditions and monitored for scoliosis development. At 9-11 weeks after pinealectomy, thoracic spinal cords were removed for 2[125I]iodomelatonin binding assay, and blood was collected for serum melatonin assay at either the middle of the light period or middle of the dark period.


RESULTS
Pinealectomy in young chickens produced: (1) loss of diurnal variations in serum melatonin levels, (2) 50% incidence of scoliosis, and (3) attenuation in the diurnal variations in the receptor affinity to melatonin. No differences were detected in the serum melatonin levels or binding of spinal cord melatonin receptors between the pinealectomized chickens that had scoliosis develop and those that did not.


CONCLUSIONS
Changes are detected in melatonin receptor binding after pinealectomy. However, these changes cannot account for the reason why scoliosis develops in some chickens after pinealectomy, while it does not in others. Neither low melatonin serum level nor changes in spinal cord melatonin binding can be a sole etiologic factor in the pathogenesis of scoliosis in pinealectomized chickens.
Poon
Angela M S
AM
Department of Physiology, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China. amspoon@hkucc.hku.hk
Cheung
Kenneth M C
KM
Lu
D S
DS
Leong
John C Y
JC
D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D002940:Circadian Rhythm; D004195:Disease Models, Animal; D007457:Iodine Radioisotopes; D008550:Melatonin / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D010870:Pineal Gland / Q000601:surgery*; D044094:Receptors, Melatonin / Q000097:blood*; D012600:Scoliosis / Q000097:blood / Q000378:metabolism / Q000473:pathology*; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology*; D013904:Thoracic Vertebrae
D007457:Iodine Radioisotopes; D044094:Receptors, Melatonin; C044556:2-iodomelatonin; D008550:Melatonin