Innervation of the human minor salivary glands; immunohistochemical study for neurochemical substances.

Distributions of choline acetyltransferase (ChAT), vasoactive intestinal polypeptide (VIP), dopamine ß-hydroxylase (DBH), tyrosine hydroxylase (TH), neuropeptide Y (NPY) and the transient receptor potential cation channel subfamily V member 2 (TRPV2) were examined in the human minor salivary glands. ChAT-, VIP- and DBH-immunoreactive (-IR) nerve fibers were detected within nerve bundles and close to blood vessels and ducts in the salivary glands. Periacinar nerve fibers were commonly immunoreactive for ChAT in the Ebner's gland but infrequently in other salivary glands. Periacinar VIP-IR nerve fibers were numerous in the palatal gland, moderate in the lingual gland and relatively rare in the labial and Ebner's glands. Some TH-, NPY- and TRPV2-IR nerve fibers were also present around blood vessels and glandular acini in the palatal, lingual and Ebner's glands. Neuronal cells in the vicinity of Ebner's and lingual glands were immunoreactive for ChAT, VIP, TH and TRPV2. By confocal laser scanning microscopy, VIP- and ChAT-IR varicosities were located in the vicinity of myoepithelial and acinar cells in the minor salivary glands. The human minor salivary glands are probably innervated by parasympathetic and sympathetic nerves. Neurotransmitters including neuropeptides in these nerves are thought to be correlated to vasodilation and/or salivary secretion. Acetylcholine and VIP may regulate secretion of the saliva and its components in the salivary glands.

Distribution of neuronal cells which contain dopamine ß-hydroxylase, tyrosine hydroxylase, neuropeptide Y and vasoactive intestinal polypeptide in the human internal carotid nerve.

The human internal carotid nerve (ICN) occasionally has a swelling beneath the external opening of the carotid canal. In this study, the presence and distribution of neuronal cells were investigated in the bilateral ICNs of nine human cadavers. Among 44.4% of the cadavers, swellings were detected in the ICN. Their diameters ranged from 1.7 to 3.6 mm (average ± SD = 2.6 ± 0.7 mm). Thirty-eight percent of these swellings were large (diameter > 3 mm) and showed an oval shape. The large swelling contained many neuronal cells. However, the ICNs with or without a swelling <3 mm diameter were mostly free from neuronal cells (93.3%). Only in one human cadaver, the right ICN without a swelling had a small number of neuronal cells. By the present immunohistochemical method, ICN neurons contained catecholamine-synthesizing enzymes and neuropeptides. Dopamine-beta hydroxylase- and tyrosine hydroxylase-immunoreactivity were mostly expressed by ICN neurons. More than half of them also contained neuropeptide Y-immunoreactivity. However, vasoactive intestinal polypeptide-immunoreactive ICN neurons were relatively infrequent. Substance P- and calcitonin gene-related peptide-immunoreactive ICN neurons could not be detected. By the cell size analysis, neuropeptide Y-immunoreactive neurons were significantly smaller than neuropeptide Y-immunonegative neurons in the ICN. The present study suggests that ICN neurons have a sympathetic function in the human.

Parasympathetic neurons in the human submandibular ganglion.

The submandibular ganglion (SMG) contains parasympathetic neurons which innervate the submandibular gland. In this study, immunohistochemistry for vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), choline acetyltransferase (ChAT), dopamine ß-hydroxylase (DBH), tyrosine hydroxylase (TH), and the transient receptor potential cation channel subfamily V members 1 (TRPV1) and 2 (TRPV2) was performed on the human SMG. In the SMG, 17.5 % and 8.9 % of parasympathetic neurons were immunoreactive for VIP and TRPV2, respectively. SMG neurons mostly contained ChAT- and DBH-immunoreactivity. In addition, subpopulations of SMG neurons were surrounded by VIP (69.6 %)-, TRPV2 (54.4 %)- and DBH (9.5 %)-immunoreactive (-ir) nerve fibers. SMG neurons with pericellular VIP- and TRPV2-ir nerve fibers were significantly larger than VIP- and TRPV2-ir SMG neurons, respectively. Other neurochemical substances were rare in the SMG. In the human submandibular gland, TRPV1- and TRPV2-ir nerve fiber profiles were seen around blood vessels. Double fluorescence method also demonstrated that TRPV2-ir nerve fiber profiles were located around myoepithelial and acinar cells in the submandibular gland. VIP and TRPV2 are probably expressed by both pre- and post-ganglionic neurons innervating the submandibular and sublingual glands. VIP, DBH and TRPV2 may have functions about regulation of salivary components in the salivary glands and neuronal activity in the SMG.

Sensory neurons in the human jugular ganglion.

The jugular ganglion (JG) contains sensory neurons of the vagus nerve which innervate somatic and visceral structures in cranial and cervical regions. In this study, the number of sensory neurons in the human JG was investigated. And, the morphology of sensory neurons in the human JG and nodose ganglion (NG) was compared. The estimated number of JG neurons was 2721.8-9301.1 (average number of sensory neurons ±â€¯S.D. = 7975.1 ±â€¯3312.8). There was no significant difference in sizes of the neuronal cell body and nucleus within the JG (cell body, 1128.8 ±â€¯99.7 µâ€¯m2; nucleus, 127.7 ±â€¯20.8 µâ€¯m2) and NG (cell body, 963.8 ±â€¯225.7 µâ€¯m2; nucleus, 123.2 ±â€¯32.3 µâ€¯m2). These findings indicate that most of sensory neurons show the similar morphology in the JG and NG. Our immunohistochemical method also demonstrated the distribution of ion channels, neurotransmitter agents and calcium-binding proteins in the human JG. Numerous JG neurons were immunoreactive for transient receptor potential cation channel subfamily V member 1 (TRPV1, mean ±â€¯SD = 19.9 ±â€¯11.5 %) and calcitonin gene-related peptide (CGRP, 28.4 ±â€¯6.7 %). A moderate number of JG neurons contained TRPV2 (12.0 ±â€¯4.7 %), substance P (SP, 15.7 ±â€¯6.9 %) and secreted protein, acidic and rich in cysteine-like 1 (SPARCL1, 14.6 ±â€¯7.4 %). A few JG neurons had vesicular glutamate transporter 2 (VGLUT2, 5.6 ±â€¯2.9 %) and parvalbumin (PV, 2.3 ±â€¯1.4 %). SP- and TRPV2-containing JG neurons had mainly small and medium-sized cell bodies, respectively. TRPV1- and VGLUT2- containing JG neurons were small to medium-sized. CGRP- and SPARCL1-containing JG neurons were of various cell body sizes. Sensory neurons in the human JG were mostly free of vasoactive intestinal polypeptide (VIP), tyrosine hydroxylase (TH) and neuropeptide Y (NPY). In the external auditory canal skin, subepithelial nerve fibers contained TRPV1, TRPV2, SP, CGRP and VGLUT2. Perivascular nerve fibers also had TRPV1, TRPV2, SP, CGRP, VIP, NPY and TH. However, PV- and SPARCL1-containing nerve endings could not be seen in the external auditory canal. It is likely that sensory neurons in the human JG can transduce nociceptive and mechanoreceptive information from the external auditory canal. Theses neurons may be also associated with neurogenic inflammation in the external auditory canal and ear-cough reflex through the vagus nerve.