Effect of Substance P on Pulmonary Resistance and Dynamic Pulmonary Compliance in the Anaesthetized Cat and Guinea‐pig

The effect of substance P, acetylcholine, and histamine on pulmonary resistance (RL) and on pulmonary dynamic compliance (CDYN) was studied in the anaesthetized cat and guinea-pig. In the anaesthetized guinea-pig, substance P (0.1-1.0 microgram/kg) acetylcholine (1.0-10 microgram/kg), and histamine (1.0-10.0 microgram/kg) produced a dose-dependent increase in RL and decrease in CDYN. In the anaesthetized cat, the effect of substance P was weak on both RL and CDYN, whereas histamine (5-50 microgram/kg) produced a dose-dependent increase in CDYN, but the effect on RL was weak. The effect of acetylcholine was qualitatively the same as in the anaesthetized guinea-pig but about 10 times less effective.