SUSTAINED FOREARM VASODILATION IN HUMANS DURING MENTAL STRESS IS NOT NEUROGENICALLY MEDIATED

To evaluate the possible neurogenic influence on forearm vasodilation during mental stress (Stroop's colour word conflict test), haemodynami c and catecholamine responses were registered in 12 healthy men after axillary blockade. Forearm blood flow was measured with venous occlusi on plethysmography and forearm vascular resistance was calculated. wit h intraarterial blood pressure data. Blood samples for arterial and ve nous adrenaline and noradrenaline determinations were collected. Basal forearm blood flow increased markedly after axillary blockade. but th e relative responses of forearm blood flow and forearm vascular resist ance to mental stress were the same as in previously studied unblocked individuals (about. +125% and about -40%, respectively). There was no increase in noradrenaline overflow from the forearm during mental str ess in the nerve blocked arm. Heart rate and arterial systolic pressur e responses as well as catecholamine responses to mental stress were a ugmented in the nerve blocked group. presumably due to a certain arous al caused by the experimental procedure. Increases in forearm blood fl ow and decreases in forearm vascular resistance during infusion of adr enaline were similar in the nerve blocked and in the control arm. In c onclusion, vasodilation in the forearm during mental stress occurs in the absence of nervous control of the vascular bed. The reactivity of the vascular bed to an exogenous vasodilator (adrenaline) remains unch anged after axillary blockade.