in isolated rat atria bicuculline ( 10-300 microm ) induced potent positive inotropic and negative chronotropic effects which were not antagonized by propranolol ( 1 microm ) , 6-hydroxydopamine pretreatment ( 50 mg/kg i.v . twice ) , ranitidine ( 3 microm ) or atropine ( 1 microm ) .
C1372752
negative
C0033497
propranolol