Reduced adrenal cortical sensitivity to ACTH in lambs with cut splanchnic nerves

The possibility that the sensitivity of the adrenal cortex to endogenous ACTH may be affected by splanchnic nerve activity has been investigated in conscious, weaned, 5- to 8-month-old lambs. The animals were atropinized (0.5 mg/kg) and tested with an i.v. infusion of noradrenaline (333 ng/kg per min for 10 min), which produced a significant rise in the mean concentration of both ACTH and cortisol in the arterial plasma. In lambs tested at least 7 days after section of both splanchnic nerves, just below the diaphragm, the rise in plasma ACTH concentration was significantly greater, and that in plasma cortisol significantly less, than in control lambs. The mean plasma ACTH and cortisol concentrations were linearly related to one another in both groups (r = 0.93 and 0.92) but the sensitivity of the adrenal cortex to the steroidogenic action of ACTH appeared to have been roughly halved 1 week after bilateral splanchnic nerve section.