the four tachykinins elicited a concentration-dependent contraction in tracheal smooth muscle devoid of epithelium , with the following order of potency : nka greater than l 363851 greater than nkb greater than sp , ( ec50 1.0 x 10 ( -9 ) m , 3.2 x 10 ( -9 ) m , 7.5 x 10 ( -9 ) m and 1.2 x 10 ( -7 ) m , respectively ) , which suggests that nk2 receptors predominate in airway smooth muscle .
C0039241
tachykinins
C0038585
sp