Change with dose of the cardiovascular and respiratory responses to chemical stimulation of the small intestine receptors

Abstract

In experiments on acute cat preparations in which nicotine and acetylcholine were injected into the fluid perfusing the intestine, which retained only nervous connection with the body, the reactions induced depended only on the dose of the chemical substances. Low doses (0.01–1.0 γ) caused a slight drop in arterial pressure, and a fall in heart and respiration rates. On the other hand, large doses of 5–100 γ of these substances caused an increase in arterial blood pressure and a rise in pulse and respiration rates. The intensity of the reaction increased with increasing dose only up to a certain limit, which was not the same for the different responses; after the maximum has been reached, the blood pressure and respiration responses fall and the cardiac reaction becomes reversed, so that the heart rate falls in response to the action of nicotine upon the intestinal receptors.