Development of the spine following pinealectomy in growing rats

Idiopathic scoliosis is the most frequent spine deformity in the frontal pl ane in man. Etiology of the disease, despite of long-lasting efforts to dis close it, remains unknown. This experimental study was aimed at assessing t he spine development in growing rats following pinealectomy and drawing con clusions concerning the pathology of idiopathic scoliosis in man. The authors evaluated the development of scoliosis in 22 rats (Rattus norve gicus v. alba f. domestica) following surgical pinealectomy. Rats were oper ated on after intraperitoneal anesthesia at 3 to 5 weeks of age. Incidence of scoliosis was radiographically determined 8 and 16 weeks after the surge ry. The rats were then euthanized and the excision of corpus pineale was co nfirmed histologically by an independent pathologist who examined their iso lated brains. In all, 8 adult rats in a good state of health served as cont rols for determining the normal physiological spine curvature. More rapid growth was observed in the experimental group of 22 rats after p inealectomy at the age of 3 to 5 weeks. The mean body weight after four mon ths of age reached 425 g. Cervicothoracic lordosis (from C2 to T7) and thor acolumbar kyphosis (from T7 to S1) measured -40 degrees and +25 degrees on average, respectively. Scoliosis was found in 5 rats (four males and one fe male), i.e. 22.7% of cases out of 22 animals evaluated at the end of the st udy. 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 degrees (from 9 degrees to 14 degrees). There was no scoliosis fou nd in the control group of 8 healthy adult rats. Statistical evaluation of obtained results was performed. Evaluating the occurrence of scoliosis in e xperimental animals in comparison with the control group using Fisher's tes t we found no statistically significant relation to pinealectomy at the 5% level of significance. Student's t-test proved statistically significant di fferences (p < 0.01) between both groups as far as the thoracolumbar kyphos is was concerned. Results of the t-test were not significant for cervicotho racic 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 a naesthetics. These factors may also influence the curvature of the thoracol umbar kyphosis.