Neurogenic constriction of the superior mesenteric and femoral veins during systemic blood pressure oscillation in rabbits.

Behavior of the mesenteric and femoral veins was studied in rabbits during an arterial pressure oscillation elicited by a method that we call the "side pressure exertion experiment." A segment of the mesenteric or femoral vein with intact innervation was vascularly isolated and was perfused under an isovolumetric condition. The force of the isovolumetric constriction of the segments was recorded in terms of the intrasegmental pressure duirng arterial pressure oscillation. The intrasegmental pressure of the superior mesenteric vein indicated an alternation of marked rise and fall during the oscillation. On the other hand, the response of the femoral segment during oscillation was less phasic but was better maintained at the higher range of initial pressures than that of the superior mesenteric segment. Simultaneously with the maximum rise of systemic arterial pressure, maximum elevation by 6.1, 6.1 and 6.4 mmHg was obtained in the mesenteric vein segment at initial intrasegmental pressures of 6, 10 and 14 mmHg, respectively. In the same circumstances, the femoral vein segment indicated a maximum rise of 8.1 to 9.3 mmHg at initial pressures of 10, 18, 26 and 34 mmHg. It can be concluded that there are marked differences between the mesenteric and femoral segments in behavior during systemic arterial oscillation and in the range of bearable intrasegmental pressure. The characteristics of the two veins might be related to the difference of specific circumstances in which the respective veins send blood back to the heart.