Vagal cardioinhibition is exerted through a reduction not only in the heart rate but also in the rate of propagation of the cardiac action potential and in myocardial contractility. In several species, such effects can be produced independently by selective activation of @entity21 in identified 'fat pads'. In this study we investigate differential control of heart rate and @entity713 by two ganglionic clusters in the @entity35 , a species increasingly important in studies of cardiovascular control. Epicardial sites producing low-threshold changes in P-P and P-R interval of the ECG in an arterially perfused preparation were explored with concentric bipolar stimulating electrodes. Stimulation sites centred on two principal @entity21 , the sinoatrial (SA) ganglion at the junction of the right superior @entity4264 and right atrium, and the @entity713 at the junction of the @entity358 and left atrium. Stimulation of the SA ganglion decreased heart rate in all preparations, with little or no effect on AV conduction in one-third. Stimulation of the @entity713 consistently slowed conduction without eliciting a comparable @entity1168 . Responses survived blockade of ganglionic transmission by @entity13673 , with an enhanced chronotropic selectivity to SA ganglion stimulation, suggesting that co-excitation of preganglionic elements en passant may have contributed to the earlier mixed responses. Effective stimulation sites were precisely circumscribed and corresponded to principal ganglionic clusters confirmed histologically. We conclude that cardiac vagal @entity21 in the @entity35 show a topographical functional organisation and are amenable to investigation using the arterially perfused preparation.

Differential chronotropic and dromotropic responses to focal stimulation of cardiac vagal XXXX in the @entity35 .

@entity4264 :: ('MESH:D013479', 'Disease') :: ['vena cava'] @entity713 :: ('MESH:D054537', 'Disease') :: ['AV ganglion', 'atrioventricular conduction', 'atrioventricular (AV) ganglion'] @entity358 :: ('MESH:D008171', 'Disease') :: ['inferior pulmonary veins'] @entity13673 :: ('MESH:D014294', 'Chemical') :: ['trimetaphan'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity21 :: ('MESH:D001480', 'Disease') :: ['ganglia'] @entity1168 :: ('MESH:D001919', 'Disease') :: ['bradycardia']
@entity21 :: (MESH:D001480,Disease) :: ['ganglia']
