Effects of Guanethidine, Reserpine, and Methyldopa on Reflex Venous and Arterial Constriction in Man*

Role of the venous system in baroreceptor-mediated reflexes in man

“…With the forearm prepared in the same manner as described for the equilibration technique, the brachial cuff was rapidly inflated to 30 mm Hg, and forearm blood flow, expressed in ml/100 g of tissue per minute, was calculated from the rate of change in forearm circumference during venous occlusion (18,29). Venous tone was calculated as the ratio of increase in venous pressure to the increase in forearm volume that occurred during venous occlusion and was expressed in mm Hg/ml (17,18,29).…”

“…Venous tone was calculated as the ratio of increase in venous pressure to the increase in forearm volume that occurred during venous occlusion and was expressed in mm Hg/ml (17,18,29). Forearm vascular resistance (FVR) was calculated as the ratio of mean arterial pressure to forearm blood flow, expressed as mm Hg/ml/100 g per minute.…”

“…4 of the patients had had a StarrEdwards mitral valve prosthesis inserted 6-15 months previously. Before any of the patients were included in the study, it was first determined that each had the usual increase in venous tone in response to such standard stimuli as a deep inspiration, mental arithmetic, or application of ice to the skin (15,21,(24)(25)(26)(27)(28)(29). Venous tone was measured in each subject by the occluded limb technique recently described in detail by Samueloff, BevegArd, and Shepherd (28).…”

“…Venous tone was measured in each subject by the occluded limb technique recently described in detail by Samueloff, BevegArd, and Shepherd (28). In several subjects forearm venous tone was also measured simultaneously by either the equilibration technique (18) or the acute occlusion method (17,18,29).…”

Persistence of Reflex Sympathetic Nervous System Activity in Man on Guanethidine or Reserpine

“…[1][2][3] This decrease in sympathetic activity has been attributed to depletion of peripheral catecholamine stores. However, at least one sympathetic reflex has been reported to persist when other sympathetic responses were inhibited by guanethidine,2 indicating that the sympathetic neurotransmitter substance (most likely norepinephrine) From Circulation, Volume XXXV, February 1967 Vasoconstrictor response was not entirely absent.…”