Hemodynamic consequences of defence area stimulation and afferent somatic nerve stimulation during fentanyl-nitrous...

Stimulation of the hypothalamic defence area and activation of somatic afferents in combination with carotid baroreceptor unloading was performed in cats anesthetized with fentanyl-nitrous oxide in order to investigate the circulatory consequences in terms of regional blood flow changes. These stimulation procedures, suggested to mimic activation of central neurogenic cardiovascular control mechanisms caused by anesthesia and surgical stress, were found to induce pronounced reductions in intestinal and renal blood flow as well as in diuresis. However, administration of droperidol markedly diminished the renal vasoconstriction as well as the reduction in diuresis in the dose range 0.025--0.10 mg/kg b.w. Doses of 0.15--0.25 mg/kg b.w. virtually abolished any stimulation-induced increase in renal vascular resistance, whether elicited through activation of the defence area or somatic afferents. This dose also partly blocked the neurogenic increment of intestinal vascular resistance.