VIP AND NPY IN CANINE HEARTS - DISTRIBUTION AND EFFECT OF TOTAL AND SELECTIVE PARASYMPATHETIC DENERVATION

The hypotheses that vasoactive intestinal peptide (VIP) is evenly dist ributed throughout atrial and ventricular myocardium and is present in postganglionic parasympathetic neurons in the regions of the sinoatri al and atrioventricular nodes were tested in three groups of dogs. Neu ropeptide Y (NPY) tissue concentrations were determined in each group. In six sham dogs VIP and NPY concentrations were evenly distributed a nd were higher in atria compared with ventricles. In nine parasympathe ctomized dogs, VIP concentrations in sample sites from regions of the sinoatrial and atrioventricular nodes were comparable to those in sham -operated controls. In nine denervated dogs VIP concentrations were si gnificantly decreased in three adjacent sample sites along the atriove ntricular groove. In these dogs NPY concentrations were not detectable or were significantly decreased at all sample sites of both atria and ventricles. These data suggest that VIP neurons are evenly distribute d in atrial and ventricular myocardium but do not originate in parasym pathetic ganglia supplying the sinoatrial and atrioventricular nodes. The data also demonstrate the possible presence of extrinsic VIP neuro ns in the canine right ventricle and indicate that NPY may be a useful marker of myocardial adrenergic innervation.