We investigated whether @entity934 affects cardiac action potentials through the muscarinic M1 in addition to M2 receptors in spontaneously beating @entity19 isolated right atria. A conventional glass microelectrode technique was used for the purpose. @entity934 (3-10 microM) reduced the maximum upstroke velocity of the action potentials (Vmax), followed by an increase. It shortened action potential duration at 90% repolarization, hyperpolarized the resting membrane and decreased the rate of beating. @entity3897 (3-100 nM) concentration dependently antagonized these effects of @entity934 . @entity4140 (10 and 30 nM), a selective muscarinic M1 receptor antagonist, antagonized @entity934 (5 microM)-induced reduction of Vmax without affecting other effects of @entity934 . In addition, @entity4140 (30 nM) induced an immediate and linear acceleration of the VmaX reduced by @entity934 . In contrast, AF-DX 116 (11(  2-[(diethylamino)-methyl]-1-piperidyl  acetyl)-5,11-dihydro-6 H-pyridol[2,3-b][1,4]benzodiazepine-6-one base, 30-300 nM), a selective muscarinic M2 receptor antagonist, failed to antagonize @entity934 -induced reduction of Vmax, but abolished its increase. It antagonized the shortening of action potential duration, membrane hyperpolarization and decreased the beating rate. @entity4138 ( @entity4138 , 100 and 300 microM), a muscarinic M1 receptor agonist, reduced Vmax and prolonged action potential duration, while @entity5592 (100-300 nM), a muscarinic M2 receptor agonist, evoked reverse effects. These results suggest that @entity934 exerts a mixed effect on Vmax, consisting of a reduction and a facilitation, possibly mediated by concurrent activation of muscarinic M1 and M2 receptors, respectively, in isolated right atria of @entity19 .

Muscarinic M1 receptor activation reduces maximum upstroke velocity of action potential in XXXX right atria.

@entity19 :: ('10090', 'Species') :: ['mice', 'mouse'] @entity5592 :: ('MESH:D010095', 'Chemical') :: ['oxotremorine'] @entity4140 :: ('MESH:D010890', 'Chemical') :: ['Pirenzepine', 'pirenzepine'] @entity3897 :: ('MESH:D001285', 'Chemical') :: ['Atropine'] @entity4138 :: ('MESH:D008455', 'Chemical') :: ['McN-A-343', '4-(m-chlorophenyl-carbamoyloxy)-2-butynyltrimethylammonium chloride'] @entity934 :: ('MESH:D000109', 'Chemical') :: ['acetylcholine', 'Acetylcholine']
@entity19 :: (10090,Species) :: ['mouse']
