Differential intraarterial pressure recordings from different arteries in the rat

Intraarterial pressures were recorded from five different sites in pentobarbital anesthetized rats. Simultaneous recordings were made from the brachial artery, carotid artery, femoral artery, tail artery, and a small end-branch of the superior mesenteric artery under basal conditions and under vasoconstrictor and vasodilator influences to find out whether similar mean arterial pressures (MAP) can be recorded from the various sites. It was found that MAP of proximal arteries (brachial and carotid) is higher than the MAP recorded from more distal arteries (mesenteric, tail, and femoral). A pressure difference of 5-6 mm Hg was found to exist from the level of the carotid artery to that of the femoral artery during all experimental conditions. Our results indicate that the same artery should always be used to compare MAP between different rats. Moreover, calculations of arterial resistance (MAP/BF) of most vascular beds in the rat, using MAP values obtained from the tail or the femoral artery, as are commonly done in physiologic or pharmacologic studies, can result in slightly lower resistance values than the true resistance. To obtain true arterial resistance of any vascular bed, one has to use MAP recorded at the particular vascular bed for the calculation of resistance.