Effects of electrical stimulation of the dorsal skin on systemic and mesenteric microvascular hemodynamics in anesthetized rats

The effects of electrical stimulation of the dorsal skin area on the mesenteric arterioles were investigated in anesthetized rats by the use of an intravital microscope-television system. Changes in the diameter of the mesenteric precapillary arterioles (10-40mum in diameter) were measured with an image processor. Blood flow velocity in the mesenteric precapillary arterioles was monitored by the dual sensor method developed by the authors. Electrical,stimulation was performed through two platinum. electrodes placed at the right dorsal Th5-12 level-skin area by the use of an electrical stimulator (0.2ms, 20Hz). Continuous stimulation lasting for 30s (1-10mA) and intermittent stimulation lasting for 10min (3mA) were applied. The pressor response following the depressor response was induced by a stimulus current above 8 mA. The decrease in mesenteric blood flow velocity was induced by stimulus current above 10 mA. These responses were abolished by lidocaine injection into the subcutaneous area where the electrodes were attached. No significant change in arteriolar diameter or heart rate were induced by the stimulation for 30s. Electrical stimulation of the skin for 10 min evoked a decrease in the diameter of arterioles (-3.4+/-2%, p<0.01, n=12). In the adrenalectomized group, electrical stimulation of the skin for 10 min elicited a slight increase in the diameter (1.1+/-0.5%, n=6). It is therefore suggested that electrical stimulation of the skin for 30s reflexly evoked decreases in MAP and in blood flow velocity, and that the constriction of the mesenteric precapillary arterioles induced by the stimulation for 10min was mediated by humoral adrenaline and noradrenaline released by somato-adrenal medullary reflex.