Experience with a Doppler technique to investigate the interaction of isoprenaline and various B-adrenoceptor blocking drugs on blood vessels in the lower limb.

A Doppler technique has been used in three separate studies to measure the changes induced by increasing infusion rates of isoprenaline on blood velocity, blood flow and diameters in the femoral and posterior tibial arteries of normal volunteers and to investigate the effects of various B-adrenoceptor antagonists on these changes. Heart rate and blood pressures were also recorded. Isoprenaline produced the expected changes in heart rates and blood pressures in the volunteers and changes induced in these responses by the B-adrenoceptor antagonist were as seen by previous workers. The only expected finding was that systolic blood pressure at the ankle was decreased compared to that in the arm which was increased. Isoprenaline produced reproducible dose-dependent increases in blood velocity, blood flow and diameters in the femoral artery, but little or no effects in the posterior tibial artery. These differences may reflect the difference in distribution of these arteries, the femoral to large muscular beds and the posterior tibial artery essentially to skin vascular beds. The different effects of the B-adrenoceptor blocking drugs with different actions on B1- and B2-adrenoceptors on the responses of the Doppler measurements to isoprenaline would support the differences in distribution of the femoral and posterior tibial arteries and allow a conclusion that the muscle vascular beds contain essentially B2-adrenoceptors with respect to stimulation by isoprenaline. The results obtained in three separate studies using the Doppler technique do suggest that this non-invasive technique may be of value in investigating the physiology, and/or pharmacology of the peripheral circulation in man.