Abstract
In the present study, we examine the projections of respiratory and circulatory area of nucleus tractus solitarius (NTS) to the laryngeal vagal neurons of nucleus ambiguus (NA) in male Wistar rats by anterograde and retrograde tract-tracing methods. WGA-HRP (Sigma, 2.5%) was injected into the cervical vagus, laryngeal muscle or recurrent laryngeal nerve (RLN) separately. After 48-72 hours survival, we found most labeled vagal neurons were located within and ventrolateral to the NA and many other neurons were found in the DMV in the cervical vagus group. But HRP-labeled neurons were located mainly in the NA area in laryngeal muscle or RLN injection groups. Biotin-conjugated dextran (BD, Molecular Probes, 10%, 20-40 nl) was injected into the NTS near the obex level, where profound depressor response and decrease in diaphragm activity were induced by microinjection of glutamate solution (Glu, 10 mM). Ten days later, we found many BD labeled fiber terminals and buttons, which projected from NTS, in the region of NA, bilaterally. Notice that dense fiber terminals existed in the NA area, which containing the HRP-labeled neurons innervating the laryngeal muscles. The data suggested that the NTS might play an important role in controlling the respiratory function by direct projecting to the laryngeal vagal neurons in NA. But it should be proved by anterograde & retrograde experiments in the same animal simultaneously.
Published Version
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