Neurotropic effects of substance P.

Summary. Intracisternal or intraventricular injections of small closes of highly purified Substance P elicit stimulation of respiratory frequency and amplitude in cats and rabbits. The effects on the blood pressure of injections of Substance P into the III:rd ventricle were usually small and variable. No consistent effects of moderately large doses administered intravenously were observed on the carotid occlusion test or on the effect of preganglionic stimulation on the nictitating membrane. Intraventricular injection of Substance P had no definite effect on diuresis. Substance P injected into a lateral ventricle caused a variety of symptoms of which a general inhibition of spontaneity was the most marked.