Abstract
In experiments by Wilhelmj et al. on the effects of dietary and psychomotor stress on the etiology of essential hypertension normal dogs were first used, then totally sympathectomized dogs, then partially sympathectomized dogs (1,2,3). It was found that exposure to the dietary and psychomotor stresses did not or could not produce in normal or in healthy totally sympathectomized dogs a sustained elevation of blood pressure. Indeed, totally sympathectomized dogs were slightly more resistant than normal dogs to dietary stress, and they also failed to show residual changes in blood pressure (2) while totally sympathectomized dogs reacted almost like normal dogs to psychomotor stress (3); psychomotor stress could not produce hypertension in otherwise normal dogs (3).* But animals with sympathetic imbalance, produced by a unilateral paravertebral sympathectomy with denervation of the adrenal gland of the same side, were very sensitive to these stresses and tended to develop marked elevations of blood pressure of long duration. Administration of a ganglionic blocking agent reduced the blood pressure to or below control values, but the elevated pressures returned as the drug effect disappeared. The elevated pressures were also lowered to or below the control values by correction of the sympathetic imbalance by complete removal of the remaining sympathetic chain and denervation of the homolateral adrenal gland.