Catecholamines and Hypertension

To the Editor: I read with great interest the study by Louis et al. on plasma norepinephrine levels in essential hypertension.1 Recent experiments in our laboratory on normal and adrenalectomized rats support some of their findings.2 In rats treated with urethane, which itself substantially reduces plasma catecholamines, intravenous administration of hexamethonium chloride (10 mg per kilogram) and atropine sulfate (1 mg per kilogram) reduces levels of circulating catecholamines to less than 1/3 of their control values in 5 minutes. This reduction is accompanied by a fall in blood pressure. When these animals are treated with scorpion venom, a powerful adrenergic-releasing.