leucine-enkephalin ( le ) at 10 ( -8 ) m reduces the maximum chronotropic response of isolated spontaneously beating rat atria to exogenously added ( - ) -norepinephrine ( ne ) by approximately 27 % , with no effect on the ne ed50 ( 1.5 x 10 ( -7 ) m ) for positive chronotropy .
C0028351
ne
C1372804
positive chronotropy