Effect of pentobarbital anesthesia and surgery on the control of arterial pressure and mesenteric resistance in cats: role of vasopressin and angiotensin.

We compared the effects of pentobarbital-induced anesthesia and major surgery (laparotomy) on the mesenteric resistance vessels and arterial pressure of cats. Intravenous infusion of sodium pentobarbital (30 mg/kg over 30--60 min) into conscious and unrestrained cats caused only a small increase in superior mesenteric arterial conductance and a small fall in femoral arterial pressure. In contrast to the effects of pentobarbital, major surgery caused marked mesenteric vasoconstrictor and pressor responses. Under these conditions, acute hypophysectomy and infusion of [Sar1, Ala8]angiotension II (saralasin) caused mesenteric conductance and arterial pressure to return towards presurgery control values. The results suggest that the high arterial pressure and constricted state of the mesenteric bed seen in acute experiments appears to be related to surgical stress rather than pentobarbital-induced anesthesia and that both the vasopressin system and the renin-angiotensin system appear to play important roles in the control of arterial pressure and the mesenteric resistance vessels under these conditions.