Morphological and quantitative study of the intrinsic nerve plexuses of the canine trachea as revealed by immunohistochemical staining of protein gene product 9.5

Abstract

Background: The ganglionated nervous plexuses in the trachea play an important role in the regulation of respiration. Although the tracheal tissue of the dog has frequently been used in physiological and pharmacological studies, little is known about the morphology of the intrinsic nervous plexuses in the dog trachea and quantitative data about the ganglia and nerve cell bodies are lacking. The structure of the nervous plexuses and detailed morphometric data about the intrinsic neurons of the dog have not previously been reported.Methods: The structure of the intrinsic nerves in the dog trachea was examined by a combination method of digestion with KOH and immunohistochemical ataining of protein gene product 9.5. In addition, areas of nerve cell profiles, numbers of nerve cell bodies per ganglion and densities of nerve cell bodies per ganglion were estimated in preparations from five dogs.Results: In the dog trachea, the peritracheal plexus, outer submucosal plexus, inner submucosal plexus, and mucosal plexus were identified from adventitia to epithelium in that order. The peritracheal plexus, situated in the lamina adventitia of the trachea, consisted of thick nerve bundles that were densely distributed in the membranous wall. The peritracheal plexus contained ganglia with round or oval nerve cell bodies. In the trachealis muscle, the intramuscular plexus, which was a well-developed, three-dimensional nervous network, was observed. It did not include ganglia and consisted of inter-and intrafascicular networks. The outer submucosal plexus was observed as small clusters in the inside of the trachealis muscle. A few round nerve cells were observed in the outer submucosal plexus as small clusters. The ganglionated inner submucosal plexus was identified in the superficial layer of the submucosal layer. A finer meshwork, namely, the mucosal plexus, was observed in the lamina propria. Among the entire length of the trachea, we counted 2,134-2,873 ganglia (average, 2,389) and 13,902-24,232 nerve cell bodies (average,18,461) were counted in the peritracheal plexuses of five dogs. The densities of ganglia and nerve cell bodies were high near the carina and low near the thoracic inlet. The number of nerve cell bodies per ganglion was estimated as 6.5-8.8 (average, 7.7). The average maximum area of nerve cell profiles was 522 ؎ 223 m 2 .Conclusions: The structure of the tracheal plexuses in the dog is more complex than those in other smaller animals. The constitution of the plexuses seems to be that of the intestine. The numerous nerve cells in the peritracheal plexus in the adventitia can be expected to play important roles in airway regulation and in the pathogenesis of tracheal collapse.

Anatomical characteristics of tonic and phasic postganglionic neurons in guinea pig bronchial parasympathetic ganglia

“…1) and could be located without staining in most preparations. Furthermore, ganglia were distributed over the entire surface of the primary bronchus and not in separate plexuses, as reported for guinea pig (Lees et al, 1997;Canning and Fischer, 1997;Fischer et al, 1998), cat (Mitchell et al, 1989), dog (Yamamoto et al, 1998), and ferret (Coburn and Kalia, 1986;Dey et al, 1996;Dey et al, 1999) tracheal ganglia. Thus, the guinea pig bronchial nerve plexus provides an excellent preparation for characterization of physiological Myers, 1998), pharmacological Undem, 1993, 1996), and anatomical properties of parasympathetic innervation in smaller airways.…”

“…The average number of neuronal cell bodies within guinea pig bronchial ganglia differed from those reported for mouse tracheal ganglia (Cassell et al, 1986), but were similar to the number in ferret (Baker et al, 1986), dog (Yamamoto et al, 1998), or rat (Chiang, 1993) tracheal ganglia. In the guinea pig trachea, ganglia contain 2 to 30 neurons (Baluk and Gabella, 1989;Lees et al, 1997).…”

“…The neurons in the ganglia were usually in a single layer and tightly packed within a perineural sheath, similar to ganglia in the intrinsic plexus of the guinea pig trachea (Baluk et al, 1985;Lees et al, 1997). By contrast, neurons in ganglia on the mouse trachea (Chiang and Gabella, 1986), on the inlet nerve trunks of the guinea pig trachea (Lees et al, 1997), in dog paratracheal plexus (Yamamoto et al, 1998), and the longitudinal nerve of the ferret trachea (Baker et al, 1986;Coburn and Kalia, 1986) are loosely arranged around the nerve trunk and are more spherical in shape. The density of the perineural sheath aided in locating the ganglia in the unstained preparation.…”

“…Guinea pig lower airways have been extensively used to study airway hyperractivity and neuronal control of airway smooth muscle Dey, 1994). Based on the vital role played by smaller airways in regulating air flow to the lungs, it is therefore surprising that there have been no studies directly investigating the morphology of parasympathetic neurons in the guinea pig bronchi; studies hitherto in guinea pig (Baluk et al, 1985;Lees et al, 1997), rat (Chiang, 1993), ferret (Coburn and Kalia, 1986;Dey et al, 1996), cat (Mitchell et al, 1989), and dog (Yamamoto et al, 1998) have focused on neurons in tracheal ganglia. Thus, the purpose of this study was to determine the location and anatomical characteristics of bronchial parasympathetic ganglia neurons and to understand how these anatomical properties may relate and contribute to their integrative physiological function.…”

Substance P and neurokinin-1 receptor expression by intrinsic airway neurons in the rat

“…Section 1734 solely to indicate this fact. chea from the neighboring tissue was not designed to preserve the tracheal nerves or the longitudinal trunk parasympathetic ganglia attached to these nerves (2,52). At least in the ferret, the majority of the neurons in these ganglia are cholinergic and lack substance P expression (7).…”