Tail artery blood flow measured by chronically implanted Doppler ultrasonic probes in unrestrained conscious rats

We describe a surgical procedure for chronically implanting a Doppler ultra sonic probe around the tail artery of the rat to measure phasic flow veloci ty in the tail artery of the unrestrained conscious rat. The phasic tail Ro w signal is highly correlated with the simultaneously recorded superior mes enteric flow signal (range 0.70-0.89 in seven rats) during vasoconstriction induced by exposure to formaldehyde vapour. In response to two quick alert ing taps on the cage, tail flow velocity fell from 20 +/- 2 to 7 +/- 1 cm/s (P < 0.01) and mesenteric flow fell from 30 +/- 5 to 25 +/- 3 cm/s (P < 0. 05), with the fall in tail flow being significantly greater than the fail i n mesenteric flow (P < 0.05, n = 7 rats). In anesthetized rats, the phasic tail flow signal was highly correlated with phasic arterial pressure (range 0.71-0.83 in seven rats). The ability to reliably measure phasic arterial tail Row in the conscious unrestrained rat should facilitate experimental s tudies of brain pathways regulating now to this principally cutaneous vascu lar bed in different physiological situations. (C) 2001 Elsevier Science B. V. All rights reserved.