Distribution of alpha-synuclein in the rat cranial sensory ganglia, and oro-cervical regions

Background: Alpha-synuclein (Syn), an unfolded soluble cytosolic protein, is known as a disease associated protein in the brain. However, little is known about distribution of this protein in the peripheral nervous system. In this study, expression of Syn was investigated in the sensory ganglia of the cranial nerves V, IX and X. Methods: To analyze distribution of Syn and its co-expression with calcitonin gene-related peptide (CGRP) or the transient receptor potential cation channel subfamily V member 1 (TRPV1), immunohistochemical techniques were used in the rat cranial sensory ganglia and their peripheral tissues. Results: Syn-immunoreactive (-ir) neurons were abundant in the sensory ganglia of the petrosal (56.7%), jugular (28.3%) and nodose ganglia (82.5%). These neurons had small to medium-sized cell bodies (petrosal, mean +/- S.D. = 667.4 +/- 310.8 mu m(2); jugular, 625.1 +/- 318.4 mu m(2); nodose, 708.3 +/- 248.3 mu m(2)), and were distributed throughout the ganglia. However, the trigeminal ganglion was mostly free of Synir neurons. By double and triple immunofluorescence staining, Syn-ir neurons co-expressed CGRP and TRPV1 in the petrosal and jugular ganglia. Syn-immunoreactivity was expressed by nerve fibers in the epithelium and taste bud of oral and cervical viscerae. These nerve fibers were abundant in the nasopharynx, epiglottis and laryngeal vestibule. Some taste bud cells were also immunoreactive for Syn. In addition, Syn-ir nerve fibers were detected in the vicinity of macrophages, dendritic cells and Langerhans cells. Conclusions: Syn was abundant in the visceral sensory neurons but not in somatic sensory neurons. This protein may play a role in nociceptive and chemosensory transduction in the glossopharyngeal and vagal sensory ganglia. It is possible that Syn has a function about the immune mechanism of the upper air way. (C) 2021 Elsevier GmbH. All rights reserved.

Automated summary

The study revealed abundant expression of alpha-synuclein in sensory ganglia, with co-expression with calcitonin gene-related peptide and transient receptor potential cation channel subfamily V member 1. Immunoreactive nerve fibers were found in oral and cervical viscerae, as well as in the upper airway, potentially playing a role in nociceptive and chemosensory transduction.