Vasoactive Intestinal Polypeptide Immunostaining Research Articles

Decreased VIP and VPAC2 receptor expression in the biological clock of the R6/2 Huntington's disease mouse

Huntington's disease (HD) is a fatal genetic neurodegenerative disorder caused by a CAG triplet repeat expansion in the gene encoding the protein huntingtin. The most studied model of HD, the R6/2 transgenic mouse, replicates many features of the disease. In addition to motor, cognitive, and endocrine dysfunctions, these mice exhibit a progressive disruption of circadian rhythms. This is accompanied by an altered expression of the circadian clock genes in the suprachiasmatic nucleus/nuclei (SCN), the principal circadian pacemaker in the brain. The neuropeptide vasoactive intestinal polypeptide (VIP) and its receptor VPAC2 are highly expressed in the SCN, and VIPergic signaling plays an essential role in maintenance of ongoing circadian rhythmicity. We found a marked reduction in both VIP mRNA and VPAC2 receptor mRNA, quantified by RT-PCR, as well as a decrease in VIP immunostaining in the SCN of R6/2 mice. These changes were coupled to a disruption of circadian rhythm. We observed no loss of neurons in the SCN and therefore suggest that the changes in VIP and VPAC2 receptor are due to their decreased expression. In conclusion, we propose that impaired VIPergic signaling is an additional candidate mechanism for disruption of circadian rhythms in R6/2 mice.

Vasoactive intestinal polypeptide (VIP) is not an androgen-dependent neuromediator of penile erection

The effects of castration on vasoactive intestinal polypeptide (VIP) immunostaining in human corpus cavernosum (CC) and the relationship between VIP immunostaining and erectile function were studied in patients with localised prostate cancer who had (Group 1 = castrated) or had not (Group 2 = control) undergone 3-month neoadjuvant chemical castration before radical prostatectomy. Evaluation of erectile function included medical and sexual history, physical examination, and measurement of total serum testosterone. CC biopsies were taken at the end of radical prostatectomy and samples immunostained with anti-human VIP antibody. Specific staining was quantified by image analysis and expressed in arbitrary units (AU). Chemical castration induced erectile function deterioration in 70% of patients due to loss of sexual interest and confidence in the ability of having an erection rather than reduced ability of obtaining sexually induced erections. Average VIP content was 34.5 AU in Group 1 and 39 AU in Group 2 and this difference was not statistically significant. Chemical castration does not influence VIP immunostaining of human CC, suggesting that VIP is not an androgen-dependent neuromediator of penile erection and that it can be responsible for sexually induced erections in castrated patients.

VIP innervation: sharp contrast in fetal sheep and baboon adrenal glands suggests differences in developmental regulation

Immunocytochemical technique and light microscopy were used to ascertain the relationship between vasoactive intestinal polypeptide (VIP) and tyrosine hydroxylase in fetal sheep and fetal baboon adrenal cortices and medullae at 85% of gestation. VIP immunostaining was extremely robust in fetal sheep adrenal cortical neurofibers and cells while weak in fibers and nonexistent in cells of fetal baboon. Also, tyrosine hydroxylase-immunopositive cells, present throughout the adrenal cortices of both fetal sheep and baboons, were heavily innervated by VIP-immunoreactive neurofibers in fetal sheep, but not in fetal baboons. Adrenal cortical VIP-immunopositive fibers occurred in greater ( P<0.05) frequency in fetal sheep than in fetal baboons (14.82±3.10 vs. 0.84±0.26 fibers/field), were larger in diameter (2.93±0.34 vs. 0.93±0.07 μm) and ran for longer distances in the plane of section (127.85±5.16 vs. 74.53±4.93 μm). VIP immunogenicity in cells (ganglion and chromaffin) and fibers was robust in fetal adrenal medulla of sheep while nonexistent in baboons. VIP fibers in fetal sheep medulla were smaller in diameter compared to fetal sheep cortex (1.22±0.13 vs. 2.93±0.34 μm, P<0.05), but not compared to extrinsic nerve fibers (1.30±0.09 μm). We hypothesize that in fetal sheep of this age, medullary neurofibers derive primarily from extrinsic sources while cortical fibers arise from cortical ganglion cells. We conclude that at 85% of gestation the potential for VIP neural control of paracrine (e.g., glucocorticoid/catecholamine) interactions in both adrenal cortex and medulla is much greater in fetal sheep compared to fetal baboons.

Electron-immunocytochemical studies of perivascular nerves of mesenteric and renal arteries of golden hamsters during and after arousal from hibernation.

Electron immunocytochemistry was used to examine perivascular nerves of hamster mesenteric and renal arteries during hibernation and 2 h after arousal from hibernation. Vessels from cold-exposed but nonhibernating, and normothermic control hamsters were also examined. During hibernation the percentage of axon profiles in mesenteric and renal arteries that were immunopositive for markers of sympathetic nerves, tyrosine hydroxylase (TH) and neuropeptide Y (NPY), were increased 2-3 fold compared with normothermic and cold control animals. This increase was reduced markedly only 2 h after arousal from hibernation. The small percentage of nitric oxide synthase-1-positive axon profiles found in mesenteric (but not renal) arteries was also increased during hibernation and returned towards control values after arousal. In contrast, the percentage of perivascular axons immunostaining for vasoactive intestinal polypeptide (VIP), a marker for parasympathetic nerves, was reduced in mesenteric arteries during hibernation. There was no labelling of perivascular nerves for substance P in either mesenteric or renal arteries. It is suggested that the increase in percentage of TH- and NPY-immunostained perivascular nerves may account for the increased vasoconstriction associated with high vascular resistance that is known to occur during hibernation. The reduction in the percentage of axons positive for VIP in hibernating animals would contribute to this mechanism since this neuropeptide is a vasodilator.

Acinic Cell Carcinoma of the Lacrimal Gland

An 18-year-old woman underwent exenteration of the right orbit for tumor recurrence 3 years subsequent to external-beam irradiation for a lacrimal gland tumor diagnosed as an "adenocarcinoma." Light microscopy of the exenteration specimen revealed an acinic cell carcinoma of the lacrimal gland, with a predominant microcystic (latticelike) pattern of growth. Cytoplasmic vacuoles and the secretion within the microcysts stained positive with periodic acid-Schiff with and without alpha-amylase, alcian blue (at a pH of 2.5), mucicarmine, and colloidal iron with and without hyaluronidase. This histochemical staining for epithelial mucins supports the theory that the lacrimal gland, although serous in type, may also function as a modified mucus gland. There was cytoplasmic immunopositivity for keratin (CAM 5.2, KAE 1-3); immunostaining for vasoactive intestinal polypeptide was negative. Electron microscopy disclosed undifferentiated features of intercalated duct cells. We speculate that the lack of immunoreactivity for vasoactive intestinal polypeptide may be correlated with the predominantly undifferentiated intercalated duct cell features observed ultrastructurally.

Effect of hypothyroidism on vasoactive intestinal polypeptide-immunoreactive neurons in forebrain-neurohypophysial nuclei of the rat brain

We have recently reported that hypothyroidism increases immunoreactive (IR)-vasoactive intestinal polypeptide (VIP) and VIP and mRNA content in both parvocellular and magnocellular neurons of the rat, hypothalamic paraventricular nucleus (PVN). As VIP can stimulate vasopressin (AVP) secretion, we conducted an anatomical investigation to determine whether VIP-containing neurons in other regions of the brain that are involved with homeostatic mechanisms of water and salt conservation are also affected by hypothyroidism. The distribution and intensity of VIP immunostaining in neurons and fibers of the magnocellular-neurohypophysial system, including the hypothalamic PVN, supraoptic nucleus (SON) and accessory magnocellular cell groups, circumventricular subfornical organ (SFO), preoptic and anterior hypothalamus, midline thalamus, subthalamic zona incerta and posterior septal nuclei were studied using a highly sensitive immunocytochemical technique and unbiased neuronal counting methods, based on the optical dissector principle. Hypothyroidism increased the intensity of VIP immunostaining and/or the number/section, percentage and numerical density of IR-VIP neurons in the PVN, SON, nucleus circularis, periventricular preoptic nucleus of the hypothalamus and SFO. In addition, IR-VIP perikarya and/or fibers in the hypothalamic medial preoptic area and anterior periventricular nucleus, nucleus reuniens of the thalamus and dorsal fornix-triangular septal nucleus complex were also apparent in the hypothyroid animals while no immunostaining was seen in these areas in control animals. No quantitative and/or qualitative modifications in IR-VIP neurons and fibers were noted in the anterior hypothalamic area, suprachiasmatic nucleus, thalamic paraventricular nucles and subthalamic zona incerta between hypothyroid and control animals. These findings suggest an inverse relationship between thyroid hormone and VIP content and/or distribution of IR-VIP neurons in specific forebrain regions involved in the control of AVP release, extracellular fluid volume, thirst, blood pressure and anterior pituitary secretion. This raises the possibility that changes in fluid homeostasis and cardiovascular function occurring in hypothyroidism may be mediated, at least in part, by VIP-producing neurons in diverse regions of the brain.

Neurochemistry, connectivity and plasticity of small intensely fluorescent (SIF) cells in the rat superior cervical ganglion

Applying double-labelling immunofluorescence, the peptide content of solitary and clustered small intensely fluorescent (SIF) cells, identified by an antiserum to a selective membrane glycoprotein marker, synaptophysin, was correlated with the presence of catecholamines in the rat superior cervical ganglion. Most of synaptophysin-immunoreactive solitary and clustered SIF cells apparently contained dopamine (indicated by tyrosine hydroxylase-TH) but not noradrenaline (indicated by dopamine-beta-hydroxylase-DBH). Frequently, immunoreactivities for substance P or rarely, neuropeptide Y were colocalized in TH-immunolabeled cells of both types. Immunostaining for vasoactive intestinal polypeptide was found only in solitary SIF cells and was visible in TH-immunoreactive, as well as in TH-nonreactive cells. Very few solitary SIF cells were TH- and DBH-immunoreactive. Solitary and clustered SIF cells, as a rule, were encircled by leu-enkephalin-positive fibres which were also met-enkephalin-arg6-phe7-immunoreactive, indicating proenkephalin as precursor. SIF cells were additionally approached by varicose fibres which contained immunoreactivity for calcitonin gene-related peptide (CGRP) but not for enkephalins. As observed by immuno-electronmicroscopy, fibres that were immunostained for leu-enkephalin or CGRP, deeply invaginated into SIF cell somata. In addition to close membrane appositions, CGRP-immunolabeled fibres exhibited efferent synaptic contacts wih elements of SIF cell clusters. SIF cells were non-reactive to enkephalin-antisera in control ganglia and after transection of the postganglionic nerves (axotomy); but both types exhibited leu-enkephalin in preganglionically transected ganglia (decentralization) in which enkephalin-immunoreactive fibre baskets were absent. Synthesis of enkephalin in SIF cells after decentralization was confirmed by in situ hybridization demonstrating intracytoplasmic proenkephalin messenger-RNA. The findings are indicative for a differential neurochemical equipment of SIF cells in the rat superior cervical ganglion, which mainly is independent to a topographical classification. Moreover, they demonstrate the involvement of two neuropeptides in preganglionic SIF cell innervation. Finally, the observations indicate the capacity of SIF cells for proenkephalin-expression in response to preganglionic denervation.

The effects of A- and C-fiber stimulation on patterns of neuropeptide immunostaining in the rat superficial dorsal horn

The present study determines the effects of sciatic nerve stimulation at intensities that activate A-fibers alone or both A- and C-fibers on immunostaining for substance P (SP), cholecystokinin-octapeptide (CCK-8), galanin (GAL), dynorphin (DYN) and vasoactive intestinal polypeptide (VIP) in the superficial dorsal horn of the rat spinal cord. The goal of this study is to provide a more precise spatial localization of the sites or release or accumulation of these compounds in relation to specific types of stimuli. Following A-fiber stimulation, there was no significant change in immunostaining for any of these compounds. However, A- and C-fiber stimulation resulted in major changes. For SP, CCK-8, GAL and DYN there was a large and significant loss of immunostaining in medial regions of the dorsal horn. This is the area where sciatic nerve primary afferent fibers terminate and the depletion is probably correlated with activity in these fibers. By contrast, VIP immunostaining is increased in the lateral part of the supeficial cord, which is outside of the central sciatic afferent fiber terminations. This indicates that the increase is not in the fine sciatic sensory axons that are directly stimulated. As a final point, the fact that C-fiber but not A-fiber stimulation causes marked changes in the immunocytochemical distribution of all these compounds is further evidence, albeit indirect, that they are involved in nociceptive information processing.

‘Neuroendocrine’ differentiation in primary neoplasms of the liver

Thirty primary liver neoplasms (16 hepatocellular, nine biliary, and five epithelioid haemangioendotheliomas) were studied for the expression of the general 'neuroendocrine' markers, neurone specific enolase (NSE) and protein gene product 9.5 (PGP 9.5). Grimelius silver staining for neurosecretory granules and immunostaining for S100 protein, HMB-45, vasoactive intestinal polypeptide (VIP), and calcitonin were also performed. Eleven of the 16 hepatocellular carcinomas stained positively for PGP 9.5, four for NSE, six for HMB-45, and two for S100 protein. Seven exhibited granular staining by the Grimelius method; eight showed immunostaining for VIP, and two for calcitonin. Three of the five haemangioendotheliomas demonstrated positive immunostaining for PGP 9.5, and two for NSE; of the nine biliary carcinomas, two showed staining for PGP 9.5 and NSE, and four contained cells staining with the Grimelius technique. Primary neoplasms of liver may show 'neuroendocrine' differentiation and this aspect of their phenotypic expression has to be considered before predicting the site of origin of a tumour in the liver.

Lesion patterns of vasoactive intestinal polypeptide-containing neurons in the myenteric plexus induced by clamping or transsection of rat jejunum

The acute reactions of vasoactive intestinal polypeptide (VIP)-containing neurons in the myenteric plexus of the rat jejunum in response to circumferential clamping or transection/reanastomosis were evaluated in a detailed time course of up to ten days. Whereas in sham-operated controls VIP immunostaining was confined exclusively to varicose fibers, either clamping or transection induced the appearance of strongly VIP-immunoreactive beaded neuronal processes and neuronal perikarya in the oral part of the lesion one day postoperatively. After five days strongly immunostained varicose fibers orientated in the longitudinal axis of the gut towards the lesion reappeared suggestive of the onset of regenerative processes.

Immunohistochemical localization of VIP and Met-enkephalin in the rabbit submandibular and sublingual glands

The existence and distribution of vasoactive intestinal polypeptide (VIP), and Met-enkephalin pentapeptide were investigated by means of the peroxidase-antiperoxidase (PAP) technique in rabbit submandibular and sublingual glands. In the submandibular gland, VIP immunostaining was observed in some peripheral acinar cells, while in sublingual one VIP positive fibres surrounded semilunes. Ductal cells of both glands were also reactive. These findings suggested a role of VIP in regulating volume and composition of salivary secretion.