FOREARM VASODILATOR MECHANISMS DURING MENTAL STRESS - POSSIBLE ROLES OF EPINEPHRINE AND ANP

The contribution of epinephrine (Epi) to forearm vasodilator responses to mental stress was evaluated in 12 healthy men by comparing hemodyn amic and plasma catecholamine responses to mental stress and to intrav enous and intra-arterial infusions of epinephrine. Mental stress decre ased forearm vascular resistance (FVR) by 45%, increased arterial Epi from 0.23 to 0.44 nmol/l in arterial plasma, and increased forearm nor epinephrine overflow. Intra-arterial Epi infusion decreased FVR concen tration dependently by up to 43%. Intravenous Epi infusion decreased d iastolic arterial pressure and increased heart rate and systolic blood pressure dose dependently. FVR decreased by up to 39% at 4.60 nmol/l Epi in arterial plasma. The average Epi contribution to forearm vasodi lation during mental stress was calculated to be between 9 and 30%, de pending on if responses to stress were compared with intravenous or in tra-arterial Epi infusion. Arterial atrial natriuretic peptide immunor eactivity increased by 23% during stress, supporting a vasodilator inf luence, whereas vasopressin immunoreactivity was unaffected. Thus secr etion of Epi explains only part of the stress-induced forearm vasodila tion. Intravenous infusion of Epi appears to activate sympathetic coun terregulation.