CHARACTERIZATION OF THE CARBOHYDRATE CHAIN ON THE SUBSTANCE-P RECEPTOR IN THE RAT-BRAIN CORTEX - EFFECT OF LECTINS ON [H-3] SUBSTANCE-P BINDING

The characteristics of the carbohydrate chain on the rat cerebral cortical substance P (SP) receptor were studied. We examined the effects of pretreatment with three lectins (concanavalin A, wheat germ agglutinin, lens culinaris agglutinin) on the [H-3]SP binding activities. Each lectin can bind to the specific carbohydrate chain. Among these lectins, only concanavalin A inhibited specific [H-3]SP binding by reducing the affinity of the binding sites. The inhibitory action of concanavalin A was dose-dependent and diminshed by the addition of alpha-methyl-D-mannoside. The present results suggest that the rat cortical SP receptor has either a biantennary complex-type or a high mannose-type of carbohydrate chain, and that the carbohydrate chain is implicated in the SP binding activity of the SP receptor system.