Depressant Pharmacological Effects of a Component Isolated from Lettuce, Lactuca sativa

Abstract

A chemical agent with depressant effects was isolated from extracts of the stem of lettuce, Lactuca sativa L. The depressant L. sativa (DLS) component has sedative effects on motor activity and behavior of toads, Bufo marinus. Flaccid paralysis resulted after administration of high doses. The DLS component depressed striated and smooth muscle contraction in nerve-muscle preparations. This effect was antagonized by administration of calcium. The component also decreased heart rate and ventricular contraction in the normal heart or during tachycardia. Electrocardiograms revealed an arrhythmia characterized by a severe atrioventricular block after high doses. Effects of administration of the DLS component to the cerebrospinal fluid, lymph sacs and bran suggest that this compound acts mainly peripherally and does not readily cross the blood-brain barrier. The experiments further suggest that the DLS component acts by interference with basic excitatory processes common to muscular and neural tissues.