adenosine ( 10 ( -5 ) m ) produced a negative chronotropic effect , increasing escape intervals from 2669 +/- 647 to 3702 +/- 717** msec in control fibers and from 1864 +/- 329 to 2658 +/- 399** msec in tyramine ( 10 ( -4 ) m ) -treated fibers ( **p less than .05 ) , but failed to produce a negative chronotropic response in fibers pretreated with propranolol ( 10 ( -7 ) m ) .
C1372752
negative chronotropic
C0033497
propranolol