Bidirectional transport of angiotensin II binding sites in the vagus nerve

We previously showed that specific angiotensin II (Ang II) binding sites are present in the canine nodose ganglion and peripheral vagus nerve, and that unilateral removal of the nodose ganglion results in loss of binding in the ipsilateral nucleus tractus solitarii and the dorsal motor nucleus of the vagus. An association of Ang II binding sites with both afferent and efferent vagal fibers is consistent with actions of the peptide on cardiac vagal tone and the baroreceptor reflex. To investigate possible transport of Ang II binding sites, quantitative in vitro receptor autoradiography was used to visualize binding after double ligation of the peripheral process of the cervical vagus nerve. One ligature was tied 0.2 to 0.5 cm distal to the nodose ganglion; the second ligature was tied on the same nerve 1.0 to 1.5 cm from the nodose ganglion. Twenty-four hours later, high-affinity Ang II binding sites (Ka = 0.46 +/- 0.08 nM) accumulated at the first ligature (the side nearest the nodose ganglion), indicating anterograde transport. Since accumulations of similar affinity sites were seen distal to the second ligature, retrograde transport of binding sites also occurred. These data reveal the existence of a mechanism for the bidirectional axonal transport of Ang II binding sites in the cervical portion of the vagus nerve.