Abstract
The effect of complete transection or hemisection at various levels from the lumbar through the cervical spinal cord on a stress-induced change in plasma corticosterone concentration was studied in adult male pentobarbital-anesthetized rats. Stressors were a hind-leg tourniquet 1–5 days and a hind-leg break 5 or 10 days postoperatively. A rise in plasma corticosterone concentration 20 min after the onset of the stress was generally used as an index of ACTH secretion. Neither stressor stimulated ACTH secretion in rats with complete cord transection between L1 and T2. Hemisection between L1 and T10 did not consistently block ACTH secretion following ipsilateral or contralateral tourniquet or leg break, but hemisection above T10 blocked the effect of only the contralateral stressors. Complete cord transection above T2 was associated with elevated ‘basal’ plasma immunoreactive ACTH and corticosterone concentrations in unanesthetized rats. These elevations were partially suppressed by pre-treatment with dexamethasone 12 h prior to sacrifice. We conclude that both tourniquet and leg break stimulate ACTH secretion through pathways in the spinal cord. These pathways are not consistently lateralized between L1 and T10 but are contralateral to the stimulated extremity above T10.