Transneuronal induction of adrenal ornithine decarboxylase through descending spinal pathways

Induction of adrenal ornithine decarboxylase (ODC) was studied in rats that had previously undergone hemisection of the spinal cord at the C5–C6 level. Control rats were sham-operated. In the latter, the stress of immobilization produced symmetrical increases in ODC of the adrenal medulla. In rats with cord hemisection a quantitatively similar increase was observed only on the intact side, the response of adrenomedullary ODC of the lesioned side being significantly smaller. Induction of adrenomedullary ODC in hemisected rats by administration of apomorphine or of 2-deoxyglucose resulted in the same pattern of response as after immobilization. Induction of adrenocortical ODC by immobilization or apomorphine was not affected by cord hemisection. The results demonstrate the existence of both ipsilateral and contralateral components of descending spinal pathways for the induction of adrenomedullary ODC, the ipsilateral fibres exerting a preponderant effect.