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.