ROLE OF DESCENDING SPINAL PATHWAYS IN THE REGULATION OF ADRENAL TYROSINE-HYDROXYLASE

The effects of hemisection of the spinal cord of rats were studied with respect to (a) the ambient level of tyrosine hydroxylase activity of the adrenals bilaterally and (b) the inducibility of the enzyme when the animal is stressed by immobilization or is treated with repeated injections of apomorphine. Three days after surgery the adrenal of the intact side contained increased enzymatic activity at rest and showed an increased response to immobilization. The reverse occurred for the adrenal gland of the sectioned side. After apomorphine administration induction of the enzyme occurred, but to a smaller extent than in sham-operated animals. As previously shown with other parameters of central sympathetic function, the facilitatory and inhibitory components of descending supraspinal pathways (both ipsi- and contralateral) are involved in the regulation of preganglionic neuronal outflow. © 1979.