Effect of substance P on mechanical and myoelectrical activities of stomach and small intestines in conscious dog

The effect of Substance P (SP) on the intestine in situ of the dog was investigated. Five female dogs were used. At the same time, mechanographic recordings, using balloon kymography, were taken, while the myoelectric activity was recorded by means of electrography. Differences in SP action on the mechanogram and electromyogram of the stomach and the small intestines were reflected in the following phenomena: (a) SP in the doses used was less active on the ileum than on the stomach; (b) SP increased basal tonus but inhibited peristaltic contraction; (c) SP acted predominantly on spike discharges in the electromyogram. These results are likely to support the assumption that SP acts as a physiological modulator of smooth muscle activity.

[Supression of angiotensin II-induced contraction of the isolated guinea pig ileum by alveolar surfactants (author's transl)]

The guinea pig alveolar surfactant reduces the contraction of the isolated guinea pig ileum, induced by Angiotensin II. It is tentatively proposed, that the surfactant system suppresses the reactivity of lung blood vessels towards contacting stimuli.