THE EFFECT OF ADRENALECTOMY AND HYDROCORTISONE ON RESPONSES TO NOREPINEPHRINE AND STIMULATION OF THE CARDIOACCELERATOR NERVE

The influence of the lack and an excess of adrenal cortical hormones on the chronotropic and pressor responses to exogenously administered and endogenously released norepinephrine (NE) has been examined in two types of experiments in dogs. In one type of experiment the chronotropic and pressor responses to intravenous NE and cardiac sympathetic nerve stimulation were measured in six adrenalectomized (10 days before the experiment) dogs before and at least 60 min after 4.7 to 8.7 mg/kg of hydrocortisone. Responses were compared with those seen in a control group. In a second type of experiment, the chronotropic and pressor responses to intravenous NE were studied in 10 control dogs before and 30 and 120 min after either placebo or 50 mg/kg of hydrocortisone. The absence or excess of adrenal corticoids did not alter the pressor or chronotropic responses to intravenous or nerve-released NE. These data suggest that the influence of adrenal cortical hormones on in vivo cardiovascular responses to catecholamines has been overemphasized.