Development of the spine following pinealectomy in growing rats

Abstract

Idiopathic scoliosis is the most frequent spine deformity in the frontal plane in man. Etiology of the disease, despite of long-lasting efforts to disclose it, remains unknown. This experimental study was aimed at assessing the spine development in growing rats following pinealectomy and drawing conclusions concerning the pathology of idiopathic scoliosis in man. The authors evaluated the development of scoliosis in 22 rats (Rattus norvegicus v. alba f. domestica) following surgical pinealectomy. Rats were operated on after intraperitoneal anesthesia at 3 to 5 weeks of age. Incidence of scoliosis was radiographically determined 8 and 16 weeks after the surgery. The rats were then euthanized and the excision of corpus pineale was confirmed histologically by an independent pathologist who examined their isolated brains. In all, 8 adult rats in a good state of health served as controls for determining the normal physiological spine curvature. More rapid growth was observed in the experimental group of 22 rats after pinealectomy at the age of 3 to 5 weeks. The mean body weight after four months of age reached 425 g. Cervicothoracic lordosis (from C2 to T7) and thoracolumbar kyphosis (from T7 to S1) measured -40° and +25° on average, respectively. Scoliosis was found in 5 rats (four males and one female), i.e. 22.7% of cases out of 22 animals evaluated at the end of the study. We found left-hand curvatures four times with the apex once between T4-T5, once between T12-T13 and twice between L3-L4. In the case of one right-hand curvature it was between T10 and T11. The mean scoliosis value was 10.8° (from 9° to 14°). There was no scoliosis found in the control group of 8 healthy adult rats. Statistical evaluation of obtained results was performed. Evaluating the occurrence of scoliosis in experimental animals in comparison with the control group using Fisher's test we found no statistically significant relation to pinealectomy at the 5% level of significance. Student's t-test proved statistically significant differences (p < 0.01) between both groups as far as the thoracolumbar kyphosis was concerned. Results of the t-test were not significant for cervicothoracic lordosis. Our results indicate that the pineal body may play a role in the origin and development of idiopathic scoliosis in rats, though we cannot exclude the influence of peroperative bleeding, brain hypoxia or metabolic effects of anaesthetics. These factors may also influence the curvature of the thoracolumbar kyphosis.