Impaired function of aorta and perivascular adipose tissue in IL-18-deficient mice.

IL-18 is ubiquitously produced by both hematopoietic and non-hematopoietic cells. The present study examined the thoracic aorta, including the surrounding perivascular adipose tissue (PVAT), of IL-18KO mice from functional and histological perspectives. IL-18KO mice exhibited raised blood pressure compared with wild-type mice. Echocardiographic examination showed a thickened vascular wall and narrowed vascular diameter of the aorta. Examination by the Magnus test demonstrated dysfunction of endothelial cells (ECs) in the IL-18KO thoracic aorta and impairment of the anticontractile function of IL-18KO PVAT. Histological examination showed no inflammatory lesions in the aorta but indicated progressive fibrosis in the vessel and conversion of PVAT from brown adipose tissue-like features to white adipose tissue-like features. Electron microscopic observation suggested several deformed mitochondria in the aorta and vacuole-like structures in ECs from IL-18KO mice. In addition, activity of complex IV was lower and production of reactive oxygen species was augmented in the mitochondria of IL-18KO aorta. Although expression of LC3 B was higher, rapamycin-induced autophagy flux was impaired in the IL-18KO PVAT. Moreover, Western blot analysis revealed that LAMP 1/2 was increased in IL-18KO PVAT, and measurement of cathepsin-D activity indicated decreased levels in IL-18KO PVAT. The IL-18KO thoracic aorta thus showed defects in physiological functions related to histological alterations, and the inflammasome/IL-18 system was suggested to play a protective role in cardiovascular cells, probably through quality control of mitochondria via promotion of autophagosome/autophagolysosome formation.NEW & NOTEWORTHY IL-18 deficiency caused aortic abnormalities in terms of morphology and functions in parallel with an accumulation of damaged mitochondria and anomalous turnover of protein complexes, such as PGC-1 and LAMP1 and -2 in PVAT. These findings suggested that IL-18 plays roles in maintaining the homeostasis of vessels and PVAT around the aorta, possibly by promoting autophagy.

Interleukin-18-deficient mice develop hippocampal abnormalities related to possible depressive-like behaviors.

Interleukin-18 (IL-18) is an inflammatory cytokine linked to major depressive disorder (MDD). MDD is closely related to metabolic disorders, such as diabetes mellitus (DM) and obesity. Moreover, DM is associated with cognitive impairment and promotes apoptosis of hippocampal cells by activating pro-apoptotic and inhibiting anti-apoptotic factors. IL-18-deficient (Il18-/-) mice are obese and have DM. Therefore, we hypothesized a close relationship between IL-18 and death of hippocampal cells, affecting neurogenesis related to behavioral changes such as MDD. Il18-/- male mice were generated on the C57Bl/6 background and Il18+/+ mice were used as controls. Behavioral, histopathological, and molecular responses, as well as responses to intracerebral recombinant IL-18 administration, were examined. Compared with Il18+/+ mice, Il18-/- mice had impaired learning and memory and exhibited lower motivation. In the Il18-/- mice, degenerated mitochondria were detected in synaptic terminals in the molecular layer, the polymorphic layer, and in mossy fibers in the dentate gyrus, suggesting mitochondrial abnormalities. Because of the degeneration of mitochondria in the dentate gyrus, in which pro-apoptotic molecules were upregulated and anti-apoptotic factors were decreased, apoptosis inducers were not cleaved, indicating inhibition of apoptosis. In addition, neurogenesis in the dentate gyrus and the maturity of neuronal cells were decreased in the Il18-/- mice, while intracerebral administration of recombinant IL-18 promoted significant recovery of neurogenesis. Our findings suggested that IL-18 was indispensable for mitochondrial homeostasis, sustaining clearance of degenerative neural cells, and supporting neurogenesis, normal neuronal maturation and hippocampal function.

Physiological and molecular effects of interleukin-18 administration on the mouse kidney.

BACKGROUND: The cytokine interleukin-18 was originally identified as an interferon-γ-inducing proinflammatory factor; however, there is increasing evidence to suggest that it has non-immunological effects on physiological functions. We previously investigated the potential pathophysiological relationship between interleukin-18 and dyslipidemia, non-alcoholic fatty liver disease, and non-alcoholic steatohepatitis, and suggested interleukin-18 as a possible novel treatment for not only these diseases but also for cancer immunotherapy. Before clinical application, the effects of interleukin-18 on the kidney need to be determined. In the current study, we examined the kidney of interleukin-18 knockout (Il18-/-) mice and the effects of interleukin-18 on the kidney following intravenous administration of recombinant interleukin-18. METHODS: Il18-/- male mice were generated on the C57Bl/6 background and littermate C57Bl/6 Il18+/+ male mice were used as controls. To assess kidney damage, serum creatinine and blood urea nitrogen levels were measured and histopathological analysis was performed. For molecular analysis, microarray and quantitative reverse transcription PCR was performed using mice 6 and 12 weeks old. To evaluate the short- and long-term effects of interleukin-18 on the kidney, recombinant interleukin-18 was administered for 2 and 12 weeks, respectively. RESULTS: Compared with Il18+/+ mice, Il18-/- mice developed kidney failure in their youth-6 weeks of age, but the condition was observed to improve as the mice aged, even though dyslipidemia, arteriosclerosis, and higher insulin resistance occurred. Analyses of potential molecular mechanisms involved in the onset of early kidney failure in Il18-/- mice identified a number of associated genes, such as Itgam, Nov, and Ppard. Intravenous administration of recombinant interleukin-18 over both the short and long term showed no effects on the kidney despite significant improvement in metabolic diseases. CONCLUSIONS: Short- and long-term administration of interleukin-18 appeared to have no adverse effects on the kidney in these mice, suggesting that administration may be a safe and novel treatment for metabolic diseases and cancer.

Differential Distribution of Renal Nerves in the Sympathetic Ganglia of the Rat.

The renal nerve plexus comprises efferent and afferent fibers. It controls urine production and bodily fluid homeostasis. Efferent fibers to the kidney include sympathetic nerve fibers from their main ganglia, the prevertebral suprarenal ganglia (SrG), and the paravertebral sympathetic chain ganglia (ChG). In the present study, we examined topological innervation from these ganglia to the renal parenchymal segments of the left kidney of the rat. Fluoro-Gold was injected into the rostral or caudal poles of the left kidney. Approximately 50% of the cells in the SrG of rats injected in the rostral pole were labeled, while 60% of the cells in the ChG T13 of rats injected in the caudal pole were labeled. In addition, we performed dual-probe retrograde tracing of the nerves using two kinds of fluorescent-conjugated cholera toxins (f-CTbs) injected into the rostral and caudal poles of the left kidney. The cells labeled with each f-CTb were distributed differently in the left SrG and the lower ChGs; no dual-labeled cells were found in these ganglia. Anterograde tracing with pCAGGS-tdTomato vector transfected into the left SrG showed that tdTomato-labeled nerve varicosities extended to the cortical arterioles and urinary tubules. Immunohistochemistry revealed that they were positive to tyrosine hydroxylase and synaptophysin, suggesting that they possessed sympathetic nerve endings. Our results show that renal efferent nerves in the SrG may control the rostral part of the kidney and innervate the multiple effectors in the cortex. Anat Rec, 300:2263-2272, 2017. © 2017 Wiley Periodicals, Inc.

Interleukin-18 and its receptor are expressed in gonadotropin-releasing hormone neurons of mouse and rat forebrain.

Interleukin-18 (IL-18) is a pro-inflammatory cytokine and an important mediator of peripheral inflammation and host immune response. IL-18 functions through its binding with the IL-18 receptor (IL-18R), which consists of two chains, an IL-18-binding α chain (IL-18Rα) and a signaling ß chain. IL-18 and IL-18R are expressed in the brain; however, limited information is available on IL-18R expression and the role of IL-18 in neurosecretory cells. In the present study, we used immunohistochemical techniques to investigate the distribution of IL-18Rα and IL-18 in the hypothalamus of male mice and rats. IL-18Rα-positive and IL-18-positive perikarya and fibers were found scattered throughout the medial septal nucleus, the nuclei of the vertical and horizontal limbs of the diagonal band, the organum vasculosum of the laminae terminalis, the preoptic area, and the anterior hypothalamic area. It is well known that gonadotropin-releasing hormone (GnRH) neuronal somata and/or fibers are found in these regions. Therefore, we performed double-label immunofluorescence for IL-18Rα/IL-18 and GnRH. IL-18Rα was expressed in approximately 60% of GnRH-immunopositive perikarya, and IL-18 was distributed in all GnRH-immunopositive perikarya. These observations suggest that IL-18 exerts direct effects upon the GnRH neuron via IL-18Rα and acts on GnRH neurons through an autocrine or paracrine pathway.

Postnatal changes of interleukin-18 receptor immunoreactivity in neurons of the retrosplenial cortex in wild-type and interleukin-18 knock out mice.

Interleukin-18 (IL-18), which is involved in the inflammatory response, is also found in the cerebral cortex. IL-18 receptor-immunoreactive (IL-18R-ir) neurons are present in layer V of the retrosplenial cortex (RSC). In the adult IL-18 knock out (KO) mice, no IL-18R-ir neurons but many degenerated neurons are present in layer V of the RSC, suggesting that any changes in the neurons of layer V have occurred during postnatal development. We examined changes of IL-18R expression during postnatal development. In the wild-type mice, many IL-18R-ir neurons were present in layers II, III and VI of the RSC in 2-week-old mice, whereas they were sparsely observed in only layer III in 3-week-old mice. No IL-18R-ir neurons were present in 4- and 5-week-old mice. In older than 6-week-old mice, many IL-18R-ir neurons were present in layers V and VI. The IL-18KO mice showed IL-18R-ir neurons in layers II, III and VI at 2-weeks-old, and a few in layer III at 3-week-old mice, similar to that in the wild-type mice. No IL-18R-ir neurons were found in mice older than 4 weeks of age. Thus, IL-18 or IL-18R seem to be involved in the construction of neural circuits corresponding to events after 3-weeks of age.

Fine structure of interleukin 18 (IL-18) receptor-immunoreactive neurons in the retrosplenial cortex and its changes in IL18 knockout mice.

Interleukin 18 (IL-18) participates in the inflammatory immune response of lymphocytes. Delay in learning or memory are common in the IL-18 knockout mouse. Many IL-18-immunoreactive neurons are found in the retrosplenial cortex (RSC) and the subiculum. These neurons also contain the IL-18 receptor. We determined the location and the ultrastructure of the IL-18 receptor-immunoreactive neurons in the RSC and observed changes in the IL-18 receptor-immunoreactive neurons of the IL-18 knockout mouse. The IL-18 receptor-immunoreactive neurons were found specifically in layer V of the granular RSC. They were medium-sized neurons with a light oval nucleus and had little cytoplasm with many free ribosomes, rough endoplasmic reticulum and many mitochondria, but no Nissl bodies. The number of axosomatic terminals was about six per section. The IL-18 receptor-immunoreactive neurons were not found in the RSC in the IL-18 knockout mouse at 5 or 9 weeks of age. However, many small electron-dense neurons were found in layer V. Both the nucleus and cytoplasm were electron-dense, but not necrotic. The mitochondria and rough endoplasmic reticulum were swollen. The IL-18 receptor-immunoreactive neurons were presumed to be degenerating. The degeneration of the IL18-receptor-immunoreactive neurons in the RSC may cause the abnormal behaviors of the IL-18 knockout mice.

Interleukin-18-deficient mice develop dyslipidemia resulting in nonalcoholic fatty liver disease and steatohepatitis.

We investigated potential pathophysiological relationships between interleukin 18 (IL-18) and dyslipidemia, nonalcoholic fatty liver disease (NAFLD) or nonalcoholic steatohepatitis (NASH). Compared with Il18(+/+) mice, IL-18 knockout (Il18(-/-)) mice developed hypercholesterolemia and hyper-high-density-lipoprotein-cholesterolemia as well as hypertriglyceridemia as they aged, and these disorders occurred before the manifestation of obesity and might cause secondary NASH. The analyses of molecular mechanisms involved in the onset of dyslipidemia, NAFLD, and NASH in Il18(-/-) mice identified a number of genes associated with these metabolic diseases. In addition, molecules related to circadian rhythm might affect these extracted genes. The intravenous administration of recombinant IL-18 significantly improved dyslipidemia, inhibited the body weight gain of Il18(+/+) mice, and prevented the onset of NASH. The expression of genes related to these dysfunctions was also affected by recombinant IL-18 administration. In conclusion, this study demonstrated the critical function of IL-18 in lipid metabolism and these findings might contribute to the progress of novel treatments for NAFLD or NASH.

Brain pericytes serve as microglia-generating multipotent vascular stem cells following ischemic stroke.

BACKGROUND: Microglia are the resident macrophage population of the central nervous system (CNS) and play essential roles, particularly in inflammation-mediated pathological conditions such as ischemic stroke. Increasing evidence shows that the population of vascular cells located around the blood vessels, rather than circulating cells, harbor stem cells and that these resident vascular stem cells (VSCs) are the likely source of some microglia. However, the precise traits and origins of these cells under pathological CNS conditions remain unclear. METHODS: In this study, we used a mouse model of cerebral infarction to investigate whether reactive pericytes (PCs) acquire microglia-producing VSC activity following ischemia. RESULTS: We demonstrated the localization of ionized calcium-binding adaptor molecule 1 (Iba1)-expressing microglia to perivascular regions within ischemic areas. These cells expressed platelet-derived growth factor receptor-ß (PDGFRß), a hallmark of vascular PCs. PDGFRß(+) PCs isolated from ischemic, but not non-ischemic, areas expressed stem/undifferentiated cell markers and subsequently differentiated into various cell types, including microglia-like cells with phagocytic capacity. CONCLUSIONS: The study results suggest that vascular PCs acquire multipotent VSC activity under pathological conditions and may thus be a novel source of microglia.

Brain-derived neurotrophic factor immunoreactive vagal sensory neurons innervating the gastrointestinal tract of the rat.

We have determined whether brain-derived neurotrophic factor immunoreactive (BDNF-ir) neurons in the vagal ganglia innervate the gastrointestinal tract. Many BDNF-ir neurons were medium in size and located throughout the jugular and nodose ganglia. When Fluorogold was injected into the wall of the cervical esophagus, many retrogradely Fluorogold-labeled neurons were found in both the jugular ganglion and the nodose ganglion. When Fluorogold was injected into the body of the stomach or applied to the cut end of the subdiaphragmatic vagus nerve, numerous Fluorogold-labeled neurons were found mostly in the nodose ganglion. Double-labeling combining immunohistochemistry for BDNF and retrograde tracing with Fluorogold showed that more than 90% of the neurons in the jugular ganglion and the nodose ganglion projecting to the cervical esophagus contained BDNF-like immunoreactivity. In the cases of both Fluorogold injection into the stomach and Fluorogold application to the subdiaphragmatic vagus nerve, almost all Fluorogold-labeled neurons in the nodose ganglion contained BDNF-like immunoreactivity. These results indicated that almost all vagal sensory neurons located in either the jugular ganglion or the nodose ganglion that innervate the gastrointestinal tract are BDNF-ir neurons.

Expression of adrenergic and cholinergic receptors in murine renal intercalated cells.

Neurons influence renal function and help to regulate fluid homeostasis, blood pressure and ion excretion. Intercalated cells (ICCs) are distributed throughout the renal collecting ducts and help regulate acid/base equilibration. Because ICCs are located among principal cells, it has been difficult to determine the effects that efferent nerve fibers have on this cell population. In this study, we examined the expression of neurotransmitter receptors on the murine renal epithelial M-1 cell line. We found that M-1 cells express a2 and b2 adrenergic receptor mRNA and the b2 receptor protein. Further, b2 receptor-positive cells in the murine cortical collecting ducts also express AQP6, indicating that these cells are ICCs. M-1 cells were found to express m1, m4 and m5 muscarinic receptor mRNAs and the m1 receptor protein. Cells in the collecting ducts also express the m1 receptor protein, and some m1-positive cells express AQP6. Acetylcholinesterase was detected in cortical collecting duct cells. Interestingly, acetylcholinesterase-positive cells neighbored AQP6-positive cells, suggesting that principal cells may regulate the availability of acetylcholine. In conclusion, our data suggest that ICCs in murine renal collecting ducts may be regulated by the adrenergic and cholinergic systems.

Origin of efferent fibers of the renal plexus in the rat autonomic nervous system.

To clarify the origin of efferent nerves containing renal plexus, the retrograde neuronal tracing was utilized with a new exact closed injection system with microcapsules. The microcapsule was positioned in the rat left renal plexus, and the capsule was filled with fluoro-gold. Retrograde labeled cells were observed in the ipsilateral sympathetic trunk, especially T12 and T13, and the ipsilateral suprarenal ganglia (SrG). There were no labeled cells in the parasympathetic nuclei in medulla oblongata and sacral cords. These results indicated that the origins of efferent nerves in the rat renal plexus are almost all sympathetic ganglia, such as sympathetic trunk and SrG, and cells in other ganglia may be secondary or accessory innervations.

Calcitonin gene-related peptide immunoreactive sensory neurons in the vagal and glossopharyngeal ganglia innervating the larynx of the rat.

We have examined whether calcitonin gene-related peptide-immunoreactive (CGRP-ir) neurons in the vagal and glossopharyngeal ganglia innervate the larynx. Many CGRP-ir neurons were located mostly in the superior glossopharyngeal-jugular ganglion complex that was fused the superior glossopharyngeal ganglion and the jugular ganglion in the cranial cavity. When Fluorogold was applied to the cut end of the superior laryngeal nerve (SLN) or the recurrent laryngeal nerve (RLN), many Fluorogold-labeled neurons were found in the superior glossopharyngeal-jugular ganglion complex and the nodose ganglion. Double-labeling for CGRP and Fluorogold showed that about 80% of Fluorogold-labeled neurons in the superior glossopharyngeal-jugular ganglion complex expressed CGRP-like immunoreactivity in the case of application to the SLN, and about 50% of Fluorogold-labeled neurons expressed CGRP-like immunoreactivity in the case of the RLN. Only a few double-labeled neurons were found in the nodose ganglion. The number of the Fluorogold-labeled neurons and double-labeled neurons in the superior glossopharyngeal-jugular ganglion complex in the case of the SLN was larger than that in the case of the RLN. These results indicate that sensory information from the larynx might be conveyed by many CGRP-ir neurons located in the superior glossopharyngeal-jugular ganglion complex by way of the SLN and the RLN.

Collateral projections of the dorsal motor nucleus of the vagus nerve to the stomach and the intestines in the rat.

The vagal motor neurons project to the gastrointestinal tract by way of the gastric, celiac and hepatic branches of the vagus trunk. We have examined whether single neurons in the dorsal motor nucleus of the vagus nerve (DMV) have collateral projections to the stomach, the duodenum and the intestines using a double-labeling tracing method. Following application of Fluorogold to the cut end of the accessory celiac branch and injection of cholera toxin subunit b (CTb) into the body of stomach, many Fluorogold- and CTb-labeled neurons were found throughout the DMV. Most CTb-labeled neurons (about 90%) were also labeled with Fluorogold. When Fluorogold was applied to the cut end of the accessory celiac or the gastric branch and CTb was injected into the duodenum, many Fluorogold-labeled neurons and CTb-labeled neurons were found in the DMV. About 20% of CTb-labeled neurons were also labeled with Fluorogold. These results indicate that many neurons in the DMV send collateral projections to both the stomach and the intestines innervated by way of the celiac branch. However, many neurons in the DMV projecting to the duodenum do not project to the stomach or the intestines caudal to the duodenum.

Systemic administration of lipopolysaccharide increases the expression of aquaporin-4 in the rat anterior pituitary gland.

We investigated the effects of lipopolysaccharide (LPS)-induced endotoxemia on the expression of aquaporin-4 (AQP4) in the rat anterior pituitary gland, using the real-time polymerase chain reaction and immunohistochemistry. After intraperitoneal injection of LPS, the level of AQP4 mRNA doubled at 2, 4 and 8 hr. Immunohistochemical analysis showed an increase with time in AQP4 immunostaining in folliculo-stellate cells following LPS injection; the intensity of immunoreactivity peaked at 8 hr. At the same time, some cyst-like structures, formed by AQP4-positive cells, were observed. These findings indicate that LPS induces the expression of AQP4 in the anterior pituitary gland. The present results should provide an important key to elucidate the pathogenesis of the anterior pituitary gland during endotoxemia.

Localization in the vagal ganglia of calcitonin gene-related peptide- and calretinin-immunoreactive neurons that innervate the cervical and the subdiaphragmatic esophagus of the rat.

We have determined the localization of calcitonin gene-related peptide-immunoreactive (CGRP-ir) and calretinin-ir neurons in the vagal ganglia that innervate the cervical or subdiaphragmatic esophagus. Many CGRP-ir neurons were found exclusively in the jugular ganglion located in the cranial cavity. Calretinin-ir neurons were distributed throughout the vagal ganglia. Injection of Fluorogold into the cervical esophagus resulted in many Fluorogold-labeled neurons in the jugular and nodose ganglia. Injection of Fluorogold into the subdiaphragmatic esophagus resulted in many Fluorogold-labeled neurons, with most in the nodose ganglion. In the case of Fluorogold injection into the cervical esophagus, double-labeling combining immunohistochemistry and retrograde tracing showed that about 40% of the Fluorogold-labeled neurons in the jugular ganglion express CGRP-like immunoreactivity, and about 20% of the Fluorogold-labeled neurons in both the jugular and nodose ganglia express calretinin-like immunoreactivity. In the case of injection into the subdiaphragmatic esophagus, only a few Fluorogold-labeled neurons express CGRP-like immunoreactivity or calretinin-like immunoreactivity in the vagal ganglia. These results indicate that the cervical esophagus receives projections from many CGRP-ir neurons in the jugular ganglion and from calretinin-ir neurons in the jugular and nodose ganglia, while the subdiaphragmatic esophagus receives projections from only a few CGRP-ir and calretinin-ir neurons in the vagal ganglia.

Distribution and ultrastructure of afferent fibers in the parietal peritoneum of the rat.

The distribution and the ultrastructure of afferent fibers innervating the parietal peritoneum in the rat was studied with immunohistochemistry using an antiserum against the neuronal marker protein gene product 9.5. The immunoreactive fibers were distributed throughout the peritoneum. They generally ran straight and parallel to the intercostal nerves running in the abdominal muscles underlying the peritoneum. They sometimes branched and terminated by forming club-like endings. The number of nerve endings on the peritoneal surface was 3.25 ± 1.66 mm(-2) . Electron microscopic observations revealed both unmyelinated and myelinated nerve fibers. The unmyelinated fibers were thin and about 1 µm in diameter. Their endings formed slight swellings located just inside the peritoneal cell layer. The myelinated fibers often formed a bundle that was composed of two or three nerve fibers. Each myelinated fiber kept in contact with a Shwann cell and projected toward the peritoneal cavity. Finally, they penetrated the peritoneal cell layer to reach the peritoneal cavity. These fibers then made contacts with the peritoneal cells and became free from the myelin sheath. The ending had a club-like shape covered with collagen fibers, and contained many neurofilaments, a few mitochondria, but no synaptic vesicles. These results suggest that since the sensory endings are exposed at the peritoneal cavity, the sensory fibers are highly sensitive to somatic or nociceptive stimuli.

Non-neuronal expression of choline acetyltransferase in the rat kidney.

AIMS: Acetylcholine (ACh) has been shown to increase ion and water excretion in the kidneys, resulting in hypotension. However, no evidence of renal parasympathetic innervation has been shown, and the source of ACh acting on nephrons is still unknown. The aim of the present study was to identify ACh-producing cells in the rat kidney, by examining the expression of cholinergic agents and localization of an ACh-synthesizing enzyme, choline acetyltransferase (ChAT), in the kidney. MAIN METHODS: Adult mail Sprague-Dawley rats were used in this study. Expression of mRNA of cholinergic agents, ChAT, vesicular ACh transporter (VAChT), and high-affinity choline transporter (CHT-1), in the kidney was examined by RT-PCR. Localization of ChAT mRNA and protein was examined by in situ hybridization and tyramide-enhanced immunohistochemistry, respectively. KEY FINDINGS: RT-PCR showed the expression of ChAT, VAChT, and CHT-1. In situ hybridization demonstrated that ChAT mRNA is localized to the renal cortical collecting ducts (CCD). Immunohistochemistry showed that the ChAT-positive cells were principal cells, and that they were unevenly distributed in the tubules, and constituted approximately 15.2% of CCD in the cortex, and 3.6% and 1.5% in the outer and inner medulla, respectively. ChAT-positive immunoreactivity was localized to the apical side of principal cells, suggesting that ACh synthesis may occur in the apical compartment of these cells. SIGNIFICANCE: These results suggest that the cholinergic effects in the nephron may be mediated at least in part by ACh originating from CCD principal cells and its expression may be locally regulated in the rat kidney.

Projections of calcitonin gene-related peptide immunoreactive neurons in the vagal ganglia of the rat.

We have studied the connections of calcitonin gene-related peptide immunoreactive (CGRP-ir) sensory neurons in the ganglia of the vagus nerve. Many CGRP-ir neurons were identified in the jugular ganglion located in the cranial cavity, while fewer CGRP-ir neurons were found in the nodose ganglion located at the level of the jugular foramen. Application of Fluorogold to the cut end of the cervical vagus nerve resulted in many Fluorogold-labeled neurons in both the jugular and the nodose ganglia. Application of Fluorogold to the cut end of the subdiaphragmatic vagus nerve resulted in Fluorogold-labeled neurons mostly in the nodose ganglion with only a few labeled neurons in the jugular ganglion. Injection of Fluorogold into the heart resulted in Fluorogold-labeled neurons in both the jugular and the nodose ganglia. Double labeling combining CGRP immunohistochemistry and Fluorogold retrograde tracing showed that in cases of both the application of Fluorogold to the cut end of the cervical vagus nerve and the injection of Fluorogold into the heart, about 40% of the Fluorogold-labeled neurons in the jugular ganglion expressed CGRP-like immunoreactivity. These results indicate that many CGRP-ir neurons in the jugular ganglion innervate the cervical and thoracic visceral organs, including the heart, but only a few CGRP-ir neurons project to the abdominal visceral organs.

Immunohistochemical localization of aquaporin-4 in the rat pituitary gland.

Aquaporin-4 (AQP4) is an isoform of membrane water channel aquaporins. It is most abundant in the brain, and is believed to be expressed by astrocytes and ependymal cells. We have reported previously that rat pituitary glands express some aquaporin subtypes, including AQP4, but the precise distribution of AQP4 in the pituitary gland is not known. The present work investigated whether AQP4 immunoreactivity exists in various pituitary cell types in adult rats, using double immunofluorescent staining and confocal microscopy. In the adenohypophysis, co-labeling for S-100 protein indicated that folliculo-stellate (FS) cells and marginal layer cells in Rathke's residual pouch have extensive labeling for AQP4. Some AQP4-expressing cells also contained glial fibrillary acidic protein (GFAP) in parenchymal tissue of the anterior lobe, and cytokeratin in marginal layer cells. AQP4 was not coexpressed in any hormone-producing pituitary cells, however. In the neurohypophysis, AQP4 was expressed in some pituicytes, which have been identified as GFAP-positive. These results suggest that AQP4, which is expressed in FS cells, in marginal layer cells and in pituicytes, but not in hormone-producing cells, is important in water transfer within the pituitary gland; astrocytes and ependymal cells do the same in the brain.