An Interventriculo-Septal Ganglion Mediates The Vagal Postganglionic Control Of Contractility Of The Right Ventricle Of The Cat Heart

We investigated the role of the interventriculo‐septal (IVS) ganglion as a potential source of vagal postganglionic control of right ventricular contractility. Prior evidence demonstrated that this ganglion provides a major source of vagal postganglionic innervation to both right and left ventricles. Blockade of the IVS ganglion with hexamethonium significantly reduced the vagally‐induced changes in right ventricular contractility in the short (transverse) and long (longitudinal) axis, without affecting heart rate or blood pressure responses to left vagal stimulation. The central pathway controlling the IVS ganglion was investigated by neuroanatomical methods. The retrograde tracer, cholera toxin‐β subunit conjugated with horseradish peroxidase (CTB‐HRP) was injected into the region of the IVS ganglion and retrogradely labeled cells were found exclusively in the ventrolateral nucleus ambiguus (NA‐VL) with the greatest concentration at the level of the area postrema. These data indicate that the IVS exerts a predominant role in modulation of RV contractile function, and that its major pre‐ganglionic input arises from the left NA‐VL. This research was supported in part by NIH‐NIGMCS 2S06GM008016 to MDG, NIH‐NINDS‐SNRP 2 U54 NS039407 to MDG and VJM, NIH‐NIMH 1 R24MH067627 to MDG and VJM, 2 G12 RR003048 from the RCMI Program to MDG and NIH‐HL71830 to JLA.