Although venous capacitance has been studied in the neurally isolated tissue or in the in vitro vein segment, this is the first study of sympathetic regulation of the pressure-diameter relation in mesenteric veins in situ, where innervation is kept intact. In 25 alpha- @entity4486 -anesthetized @entity95 , mesenteric vein diameter (679 +/- 27 microns, ranges of 380-1,050 microns at initial state) and intravenous pressure were measured continuously at the same site by using videomicrometer and micropressure systems. Intravenous pressure was increased in a stepwise fashion from the baseline of 6-9 mm Hg to approximately 10, approximately 13, approximately 16, approximately 19, and occasionally to approximately 22 or approximately 26 mm Hg by occluding the portal vein with a pneumatic occluder. Each intravenous pressure was maintained for 90-120 seconds or 4-5 minutes until the diameter increase reached a plateau. Pressure-diameter curves were generated for the control state, during celiac ganglion stimulation, and during local tetrodotoxin or intravenous @entity4033 administration. Diameter was plotted as a function of pressure, and the curves were nonlinear or sigmoid. These results are different from the linear or curvilinear characteristics of the pressure-diameter or pressure-volume relation observed in the pharmacologically or chemically denervated preparation. @entity1022 and @entity4033 attenuated the sigmoid shape of the pressure-diameter curve and shifted it toward the diameter axis of the curve. On the other hand, celiac ganglion stimulation did not change the sigmoid nature of the curve but shifted the curve toward the @entity2270 .(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sympathetic tone on pressure-diameter relation of XXXX mesenteric veins in situ.

@entity4033 :: ('MESH:D018738', 'Chemical') :: ['hexamethonium'] @entity4486 :: ('MESH:D002698', 'Chemical') :: ['chloralose'] @entity1022 :: ('MESH:D013779', 'Chemical') :: ['Tetrodotoxin'] @entity95 :: ('9986', 'Species') :: ['rabbits'] @entity2270 :: ('MESH:C566610', 'Disease') :: ['volume axis']
@entity95 :: (9986,Species) :: ['rabbit']
