¡iAbstract¡j Vagal sensory neurons play an important role in the neural control of airway and other visceral organs. Regional distribution of vagal sensory neurons in the vagal ganglia that correspond to different viscera is uncertain. Horseradish peroxidase (HRP) was applied to the right thoracic vagus nerve and recurrent laryngeal nerve to be retrogradely transported to the neurons in vagal nodose and jugular ganglia. Labeling of neuronal cell bodies was visualized with diaminobenzidine reaction. Ricinus communis agglutinin-60 (RCA-60) was injected into the right thoracic vagus nerve and transported retrogradely to cause destruction of the ribosome in the vagal ganglia neuron cell bodies. The magnitude of neurogenic plasma extravasation induced by capsaicin was measured by the area density of the India ink-labeled leaky blood vessels in the trachea and bronchi. The present study demonstrated that there was no distinct localization of HRP- labeled neurons, except at the level of pharyngeal nerve that was connected to the middle of the nodose ganglion. There were approximately 42.2 % of labeled neurons in the nodose ganglion and 30.5 % in the jugular ganglion 3 days after application of HRP in the thoracic vagus nerve. After application of HRP to the recurrent laryngeal nerve, 13.3 % of labeled neurons was found in the nodose ganglion and 8.3 % in the jugular ganglion. One to two weeks after RCA injection into the thoracic vagus nerve, many cell bodies of neurons had a striking degenerative alteration and the cytoplasmic density was markedly reduced. Nissl¡¦s bodies obviously disappeared and vacuoles were the usual feature. Application of RCA-60 also inhibited the neurogenic plasma extravasation in the right bronchial tree that were reduced by 71- 89 %. It is suggested that RCA- 60 selectively destroyed the vagal sensory neurons that innervated the ipsilateral branchial tree. It is concluded that vagal nodose and jugular ganglia supplied different number of sensory neurons to the vagal branches and regulated the physiological function of the visceral organs.

Vagal sensory afferent innervation corresponds to regulation of neurogenic inflammation in the airways. Capsaicin is mostly used for stimulation of sensory nerves that induce pain and inflammatory responses. It can specifically stimulate sensory afferent nerves, inducing neurogenic inflammation in the airways. According the past studies, we have found the right thoracic vagus nerve (RTVN) and right recurrent laryngeal nerve (RRLN); branches of right thoracic vagus trunk (RTVT) mediate different degree of neurogenic inflammation by intraenous injection of capsaicin (300 nmol/ml/kg). In order to investigate the innervation from the RTVN and RRLN of rat tracheobronchi and their involvement in plasma exudation, we injected 3 £gl of capsaicin (10 mg/ml) into RTVT and denervated the RRLN or RTVN and used India ink as tracer dye to label the leaky microvessels. Our observation indicated that injection of capsaicin into the RTVT coud induce obvious plasma exudation in trachea (area density of leaky blood vessels was about 22%), but plasma exudation was significantly decreased after denervation of RRLN. The left upper side of trachea was decreased by 77.6% and the right upper side decreased by 84.5%. This phenomenon was not caused by denervation of RTVN. The results suggest that vagal nerve innervation of upper trachea mostly came from the RLN. Otherwise, capsaicin injection into the RTVT also induced neurogenic inflammation in the larynx. Experimental denervation of both superior and recurrent laryngeal nerves resulted in a decrease of plasma extravasation by 84.98%. Denervation of either RTVN or RRLN also decreased the plasma extravasation in the larynx. The evidence suggest that sensory fibers in the superior laryngeal nerve, recurrent laryngeal nerve, and thoracic vagus nerve might come from the same population of vagal ganglion sensory neurons.