The ultrastructure of the axonic terminals from the hypothalamic paraventricular nucleus (Pa) and the synapses in the dorsal motor vagus nucleus (DMV) were studied.The placement of electrolytic lesions in the Pa was carried out first,and then the injection of horseradish peroxidase (HRP) was given into the vagal nerve trunk in the neck.The results were as follows:Some Pa terminals contacted with the perikaryous and dendrites of the parasympathetic preganglionic neurons of the DMV.Most of the Pa terminals we...