Asymmetry in the vagal preganglionic control of ventricular function

Abstract

Previous data from this laboratory and others indicate that there is an asymmetry in the distribution of neurons within the nucleus ambiguus (NA) which project to different intracardiac postganglionic sites and hence influence the control of varying aspects of cardiac performance. Thus, for example, the distribution of vagal parasympathetic preganglionic (VPG) neurons which control cardiac rate is bilateral but weighted in favor of the right NA, conversely the distribution of VPG neurons which control AV conduction is weighed to the left NA. We had previously reported that the largest intracardiac ganglion is found within the septal myocardium which we refer to as the interventriculoseptal ganglion (IVSg). This ganglion provides the primary innervation to the right ventricle and contributes significantly to the left ventricle as well. We have tested the hypothesis that there may be asymmetry to the VPG control of the IVSg. CTB-HRP was injected in the pericardial space for non specific control of our tracer and these injections resulted in no detectable labeling of either VPG neurons in the NA or cardiac afferent nerve terminals in the NTS. On the other hand, when CTB-HRP was injected into the IVSg, approximately 80% of retrogradely labeled VPG neurons were observed in the left NA only, indicating that the VPG control of left and/or right ventricular function is asymmetric. No retrograde label was observed in the DMV and no retrogradely labeled axons were observed in the right vagus nerve by ultrastructural examination. NINDS-SNRP 2 U54 NS039407 to MDG and VJM, NIMH 1 R24MH067627 to MDG and VJM. Boston Scientific, Natick, MA to VJM.