The inhibition of substance P-induced histamine release from mast cells by 6, 7-dihydro-6, 8, 8, 10-tetramethyl-8H-pyrano-[3, 2-g] chromone-2-carboxylic acid (EAA).

In the presence of extracellular Ca2+, 6,7-dihydro-6,8,8, 10-tetramethyl-8H-pyrano [3, 2-g] chromone-2-carboxylic acid (EAA) had an inhibitory effect on the substance P-induced histamine release from rat peritoneal mast cells. Not only Ca2+ but also Mg2+, Sr2+ and Ba2+ were effective in enhancing the activity of EAA. Marked tachyphylaxis to EAA developed irrespective of the presence or absence of extracellular Ca2+. Cross-tachyphylaxis was observed between EAA and disodium cromoglycate (DSCG). These results indicate that the mode of action of EAA is similar, but not identical, with that of DSCG.