An electron microscopic study of acetylcholinesterase-activity and vasoactive intestinal peptide- and neuro-peptide Y-immunoreactivity of the intraepithelial nerve fibers in the nasal gland of the guinea pig

Expression of vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, and intermediate neurofilaments in nasal mucosal nerve fibers of horses without nasal disease

OBJECTIVE

To determine the distribution of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and intermediate neurofilaments in nasal mucosa of horses.

ANIMALS

6 horses without evidence of nasal disease.

PROCEDURE

Full-thickness nasal tissue specimens were obtained from the rostral portion of the nasal septum at necropsy, and fluorescence immunohistochemistry was performed to assess mucosal distribution of nerve fibers.

RESULTS

Nerve fibers with CGRP-like immunoreactivity (CGRP-Li) formed a dense subepithelial network, and a large number of fibers were found coursing between epithelial cells. Fibers with CGRP-Li were also associated with blood vessels and mucous glands. Fibers with SP-like immunoreactivity (SP-Li) had a similar distribution and density. In contrast, there were few fibers with VIP-like immunoreactivity. Fibers containing intermediate neurofilaments were prominent and appeared as large nerve fiber bundles mainly adjacent to the nasal septum but also close to mucous glands and within the lamina propria. Intermediate neurofilaments were also identified in single nerve fibers at all sites, but the density of fibers with intermediate neurofilaments did not match that of fibers with CGRP- or SP-Li.

CONCLUSIONS

The density and distribution of nerve fibers containing SP- or CGRP-Li in nasal mucosa of horses was similar to that reported for other species. However, expression of VIP in nerve fibers was low. Antibodies against intermediate neurofilaments identified many nerve fibers in nasal mucosa of horses but did not appear to identify small diameter fibers expressing SP or VIP.

Distribution, chemical coding and origin of nitric oxide synthase-containing nerve fibres in the guinea pig nasal mucosa

The distribution, chemical coding and origin of nitric oxide synthase (NOS)-containing nerve fibres in the respiratory mucosa of the nasal septum of the guinea pig were examined using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and immunohistochemistry. A rich supply of NADPH-d-positive nerve fibres was observed around blood vessels and in nasal glands where nerve fibres frequently penetrated into the epithelia of acini and intralobular ducts. NADPH-d reactivity was also found in the nerve fibres located under or within the respiratory epithelium. Combined immunofluorescence and histochemical staining of the same preparation demonstrated virtually complete overlapping of NOS immunoreactivity and NADPH-d reactivity in nerve fibres, indicating that NADPH-d can be used as a marker for NOS-containing neurons. Double-labelling using antibodies to vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) revealed that NADPH-d-positive nerve fibres frequently contained VIP or NPY, but not CGRP. Pterygopalatine ganglionectomy significantly reduced the number of NADPH-d-positive nerve fibres innervating the respiratory epithelium as well as blood vessels and nasal glands. Neither superior cervical ganglionectomy nor sensory denervation by capsaicin treatment affected the distribution of NADPH-d-positive fibres. These results indicate that NOS-containing nerve fibres innervating the respiratory epithelium as well as blood vessels and nasal glands in the guinea pig originate mainly from the pterygopalatine ganglion, and suggest that NO may play a significant role as a neurotransmitter and/or neuromodulator in the control of the respiratory epithelium as well as vasculature and nasal glands.

Histamine-induced internalization of substance P receptors in myoepithelial cells of the guinea pig nasal glands

Numerous substance P (SP) immunoreactive nerve fibers were located around submucosal glands in the guinea pig nasal mucosa. Since these SP positive nerve fibers were also positive for vasoactive intestinal polypeptide, and to a lessor extent for neuropeptide Y, they were presumed to be parasympathetic fibers. SP receptor positive structures were observed exclusively on the membrane of myoepithelial cells in normal nasal mucosa, suggesting that myoepithelial cells are targets of SP positive fibers. SP receptor-like immunoreactivity was observed associated with intracellular organella of myoepithelial cells 5 min after intranasal histamine challenge, which may indicate the molecular basis for histamine-induced nasal discharge.

Distribution of vasoactive intestinal polypeptide immunoreactive nerve fiber in the rat nasal mucosa

The distribution of vasoactive intestinal polypeptide (VIP)-immunoreactive nerve fiber of the respiratory nasal mucosa of the rat was examined by use of immunohistochemistory with light, laser confocal scanning and electron microscopy. On light microscopy, it was observed that VIP immunoreactive nerve fibers distributed under and within the epithelium in addition to around the blood vessels and glands. The laser confocal scanning microscope revealed the network of VIP-immunoreactive nerve fibers at glands, but it was denser around glands than within glands. The VIP-immunoreactive nerve fibers formed fine varicosities and was distributed below the middle portion of the epithelium. Some fibers were observed as if they were surrounding goblet cells. Electron microscopy showed that the VIP-immunoreactive nerve fibers within the epithelium were terminated as free nerve endings. Some of them were in close contact with goblet cells.

Peptidergic and adrenergic innervation of the lachrymal gland in the euryhaline turtle, Malaclemys terrapin

The controlling factors of lachrymal gland secretions were examined in the euryhaline turtle, Malaclemys terrapin. Histochemical and immunocytochemical methods were used to localize some of the possible neurotransmitters involved. There was no immunoreactivity to choline acetyltransferase, the enzyme synthesizing acetylcholine, nor did the histochemical technique for acetylcholinesterase produce positive results. Immunofluorescence and immunoperoxidase labels revealed vasoactive intestinal peptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivity in high concentrations surrounding the secretory tubules and ducts. Substance P produced a weak immunoreactivity in the interstitial space surrounding the ducts. Dopamine beta-hydroxylase, the enzyme synthesizing norepinephrine and epinephrine, was localized around the blood vessels. Immunogold labeling confirmed the presence of VIP- and NPY-like reactivity in nerve varicosities close to the basement membrane of the secretory epithelium, and double-labeling showed VIP and NPY are co-localized within the same nerve terminals. The results suggest that the secretory epithelium may be primarily under peptidergic control while the vascular system is under adrenergic control. This is possibly a new pattern of innervation for exocrine glands and may be related to the particular function of this salt gland in an euryhaline turtle.

Precise localization of VIP-, NPY-, and TH-immunoreactivities of cat laryngeal glands

The precise distribution of vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)-, and tyrosine hydroxylase (TH)-immunoreactive (ir) fibers in the cat's laryngeal glands was examined by immunoelectronmicroscopy. A relatively dense population of VIP-ir fibers was recognized close to the basal lamina of the glandular and myoepithelial cells. Some VIP-ir fibers contacted with the basal lamina and some of them pierced it and ran intercellularly in the adjoining glandular cells without making synaptic contacts with them. NPY- and TH-ir fibers were located in the vicinity of the basal lamina, but they were less abundant than VIP-ir fibers at this region. They never terminated or penetrated the basal lamina. Pattern of distribution of TH-ir fibers was similar to that of NPY-ir fibers. The estimated ratio of VIP-, TH-, and NPY-ir fibers was 20:4:1 from the density of fibers in the laryngeal glands. This value was equal between serous and mucous glandular cells, so both types of glandular cells may receive the same pattern of autonomic innervation.

Nitric oxide synthase-immunoreactive nerve fibers in the nasal mucosa of the rat

An immunohistochemical study was performed to detect the localization of nitric oxide synthase (NOS) in the rat nasal mucosa by light and electron microscopy. NOS-immunoreactive nerve fibers were observed around blood vessels and seromucous glands. They were found in the subepithelial layer and even within the epithelium. But no NOS-immunoreactivity was found in the olfactory neuroepithelium. Electron microscopy showed that NOS-immunoreactive nerve profiles were in close contact with the cytolemma of respiratory epithelial cells and acinar cells of seromucous glands. NOS-immunoreactive axon varicosities were located at a considerable distance from the smooth muscle of arterioles and small veins as well as the endothelial cells of venules and capillaries. We confirmed that NOS-containing nerves innervated the epithelium, blood vessels and seromucous glands of the nasal mucosa. These findings, collectively, suggested the possibility that nitric oxide participated in the sensory function of the epithelium, the secretory activities of the nasal gland, and the regulation of vascular tone and vascular permeability in the nasal mucosa.

Distribution of substance P immunoreactive nerve fibers in the tracheal submucosal gland of cats

Immunohistochemistry combined with electron microscopy was employed to investigate the distribution of substance P-immunoreactive (SP-IR) nerve fibers in the tracheal submucosal gland of cats. The SP-IR nerve fibers were found to form a network around the glands. Numerous varicosities were also detected within the basement membrane of the acini and secretory tubules. All the intraglandular varicosities showed close spatial contact with serous cells, mucous cells, and myoepithelial cells. Our findings suggest that substance P-induced mucus secretion from tracheal submucosal glands in cats may be caused not only by a glandular contractile response of myoepithelial cells, but also by direct stimulation to both serous and mucous cells.

Immunohistochemical and electron microscopic studies of substance P in guinea pig nasal glands

The distribution of substance P-like immunoreactive (SP-IR) nerve endings in the nasal gland of the guinea pig was studied by using histochemical techniques to detect mucous glycoprotein and immunohistochemical techniques for SP, in combination with electron microscopy. Most nasal glands were negative for both AB and periodic acid-Schiff (PAS) staining. The SP-IR nerve fibers were found to form a network around these glands. The SP-IR nerve endings were located in the region between interdigitated cytoplasmic folds of acinar cells and along the cell surface, as well as in the intercellular spaces of proximal ducts. The acini which closely contacted with SP-IR nerve endings were serous in type. Our results suggest that substance P may contribute to the regulation of serous gland secretion in the guinea pig nasal mucosa.