We have assessed the relative vasodilatory potencies of substance P, deca-substance P and nona-substance P in the canine forelimb. In pentobarbital anesthetized dogs (35 mg/kg, i.v., n=7) the right forelimb was perfused at constant flow via the brachial artery. We measured systemic, forelimb perfusion, skin and muscle small artery and skin and muscle small and large vein pressures. Brachial and cephalic blood flows were measured by timed collections of the venous effluents. The peptides were infused intra-arterially in sequentially increasing dosages of 75, 150, 300, 750 and 1500 ng/min for ten minutes at each infusion rate. Each infusion rate immediately followed the previous one. However, pressures were allowed to return to steady-state values after completion of each peptide infusion before proceeding to the next peptide. The order of peptide infusion was varied for each experiment. Substance P infusion resulted in a 48, 8, 13, 16 and 10% decrease in forelimb perfusion pressure and a 24, 10, 13, 16, and 7% decrease in systemic pressure at the above infusion rates, respectively. Infusion of deca-substance P produced 51, 6, 12, 20 and 15% decreases in forelimb perfusion pressure and 26, 6, 15, 23, and 17% decreases in systemic pressure. Nona-substance P decreased forelimb perfusion pressure 48, 6, 17, 18, and 13% and systemic pressure 15, 3, 11, 17, and 12%. Skin and muscle small and large vein pressures were only transiently altered during peptide infusion. The dilation produced by all three peptides in the forelimb was equally distributed between the skin and skeletal muscle circulations. These data indicate that substance P, deca-substance P and nona-substance P possess similar vasodilatory potencies in the canine forelimb.
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- Relative Vasodilatory Potencies of Substance P, Deca-Substance P and Nona-Substance P in the Canine Forelimb
D. E. Dobbins
M. J. Buehn
J. M. Dabney
- Springer New York
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