['Whether Mao-Bushi-Saishin-To (MBST), one of the formulas of classical Chinese medicine, is effective on 48-h passive cutaneous anaphylaxis (PCA) in rats and which substance in the formula is responsible for its inhibitory action were examined.', 'In the studies on PCA, MBST (hot water extract of the whole herbal formula), extracts of Ephedra herb (Mao), l-ephedrine and other reference drugs were orally administered immediately or at various times before or 5 min after the antigen challenge. In the experiments on anaphylactic histamine release from rat peritoneal mast cells, l-ephedrine and d-pseudoephedrine were added at 10(-4)-10(-7) g/ml at 30, 10, 3 or 0 min before antigen provocation.', 'The time course study indicated that MBST produced a prompt and long lasting inhibition of PCA. Among the constituents of Mao, l-ephedrine exerted this prompt inhibitory activity, but d-pseudoephedrine did not. Neither pseudoephedrine nor l-ephedrine prevented the anaphylactic histamine release from isolated peritoneal mast cells.'] Is l-Ephedrine a major constituent of Mao-Bushi-Saishin-To , one of the formulas of Chinese medicine , which shows immediate inhibition after oral administration of passive cutaneous anaphylaxis in rats?