Collagen XIII Is the Key Molecule of Neurovascular Junctions in the Neuroendocrine System.

INTRODUCTION: Axons of magnocellular neurosecretory cells project from the hypothalamus to the posterior lobe (PL) of the pituitary. In the PL, a wide perivascular space exists between the outer basement membrane (BM), where nerve axons terminate, and the inner BM lining the fenestrated capillaries. Hypothalamic axon terminals and outer BMs in the PL form neurovascular junctions. We previously had found that collagen XIII is strongly localized in the outer BMs. In this study, we investigated the role of collagen XIII in the PL of rat pituitaries. METHODS: We first studied the expression of Col13a1, the gene encoding the α1 chains of collagen XIII, in rat pituitaries via quantitative real-time polymerase chain reaction and in situ hybridization. We observed the distribution of COL13A1 in the rat pituitary using immunohistochemistry and immunoelectron microscopy. We examined the expression of Col13a1 and the distribution of COL13A1 during the development of the pituitary. In addition, we examined the effects of water deprivation and arginine vasopressin (AVP) signaling on the expression of Col13a1 in the PL. RESULTS: Col13a1 was expressed in NG2-positive pericytes, and COL13A1 signals were localized in the outer BM of the PL. The expression of Col13a1 was increased by water deprivation and was regulated via the AVP/AVPR1A/Gαq/11 cascade in pericytes of the PL. CONCLUSION: These results suggest that pericytes surrounding fenestrated capillaries in the PL secrete COL13A1 and are involved in the construction of neurovascular junctions. COL13A1 is localized in the outer BM surrounding capillaries in the PL and may be involved in the connection between capillaries and axon terminals.

Granular cell tumor of the neurohypophysis presenting as a third ventricle mass.

Granular cell tumors of the neurohypophysis (GCT) are rare benign neoplasms belonging, along with pituicytoma and spindle cell oncocytoma, to the family of TTF1-positive low-grade neoplasms of the posterior pituitary gland. GCT usually present as a solid sellar mass, slowly growing and causing compressive symptoms over time, occasionally with suprasellar extension. They comprise polygonal monomorphous cells with abundant granular cytoplasm, which is ultrastructurally filled with lysosomes. Here we report the case of a GCT presenting as a third ventricle mass, radiologically mimicking chordoid glioma, with aberrant expression of GFAP and Annexin-A, which lends itself as an example of an integrated diagnostic approach to sellar/suprasellar and third ventricle masses.

Imaging the Hypothalamo-Neurohypophysial System.

The hypothalamo-neurohypophysial system (HNS) is a brain peptidergic neurosecretory apparatus which is composed of arginine vasopressin (AVP) and oxytocin (OXT) magnocellular neurones and their neuronal processes in the posterior pituitary (PP). In response to specific stimuli, AVP and OXT are secreted into the systemic circulation at the neurovascular interface of the PP, where they act as hormones, but they can also behave as neurotransmitters when released at the somatodendritic compartment or by axon collaterals to other brain regions. Because these peptides are crucial for several physiological processes, including fluid homoeostasis and reproduction, it is of great importance to map the HNS connectome in its entirety in order to understand its functions. In recent years, advances in imaging technologies have provided considerable new information about the HNS. These approaches include the use of reporter proteins under the control of specific promoters, viral tracers, brain-clearing methods, genetically encoded indicators, sniffer cells, mass spectrometry imaging, and spatially resolved transcriptomics. In this review, we illustrate how these latest approaches have enhanced our understanding of the structure and function of the HNS and how they might contribute further in the coming years.

The First Pituitary Proteome Landscape From Matched Anterior and Posterior Lobes for a Better Understanding of the Pituitary Gland.

To date, very few mass spectrometry (MS)-based proteomics studies are available on the anterior and posterior lobes of the pituitary. In the past, MS-based investigations have focused exclusively on the whole pituitary gland or anterior pituitary lobe. In this study, for the first time, we performed a deep MS-based analysis of five anterior and five posterior matched lobes to build the first lobe-specific pituitary proteome map, which documented 4090 proteins with isoforms, mostly mapped into chromosomes 1, 2, and 11. About 1446 differentially expressed significant proteins were identified, which were studied for lobe specificity, biological pathway enrichment, protein-protein interaction, regions specific to comparison of human brain and other neuroendocrine glands from Human Protein Atlas to identify pituitary-enriched proteins. Hormones specific to each lobe were also identified and validated with parallel reaction monitoring-based target verification. The study identified and validated hormones, growth hormone and thyroid-stimulating hormone subunit beta, exclusively to the anterior lobe whereas oxytocin-neurophysin 1 and arginine vasopressin to the posterior lobe. The study also identified proteins POU1F1 (pituitary-specific positive transcription factor 1), POMC (pro-opiomelanocortin), PCOLCE2 (procollagen C-endopeptidase enhancer 2), and NPTX2 (neuronal pentraxin-2) as pituitary-enriched proteins and was validated for their lobe specificity using parallel reaction monitoring. In addition, three uPE1 proteins, namely THEM6 (mesenchymal stem cell protein DSCD75), FSD1L (coiled-coil domain-containing protein 10), and METTL26 (methyltransferase-like 26), were identified using the NeXtProt database, and depicted tumor markers S100 proteins having high expression in the posterior lobe. In summary, the study documents the first matched anterior and posterior pituitary proteome map acting as a reference control for a better understanding of functional and nonfunctional pituitary adenomas and extrapolating the aim of the Human Proteome Project towards the investigation of the proteome of life.

Mechanism and function of phasic firing in vasopressin-releasing magnocellular neurosecretory cells.

Magnocellular neurosecretory cells that release vasopressin (MNCVP ) from axon terminals in the neurohypophysis display a unique pattern of action potential firing termed phasic firing. Under basal conditions, only a small proportion of MNCVP display spontaneous phasic firing. However, acute and chronic conditions that stimulate vasopressin release, such as hemorrhage and dehydration, greatly enhance the number of MNCVP that fire phasically. Phasic firing optimizes VP neurosecretion at axon terminals by allowing action potential broadening to promote calcium-dependent frequency-facilitation, at the same time as preventing the secretory fatigue caused by spike inactivation that occurs during prolonged continuous stimulation. This review provides an update on our mechanistic understanding of these processes and highlights important gaps in our knowledge that must be addressed in future experiments.

Neuroendocrine changes in the hypothalamic-neurohypophysial system in the Wistar audiogenic rat (WAR) strain submitted to audiogenic kindling.

The Wistar audiogenic rat (WAR) strain is used as an animal model of epilepsy, which when submitted to acute acoustic stimulus presents tonic-clonic seizures, mainly dependent on brainstem (mesencephalic) structures. However, when WARs are exposed to chronic acoustic stimuli (audiogenic kindling-AK), they usually present tonic-clonic seizures, followed by limbic seizures, after recruitment of forebrain structures such as the cortex, hippocampus and amygdala. Although some studies have reported that hypothalamic-hypophysis function is also altered in WAR through modulating vasopressin (AVP) and oxytocin (OXT) secretion, the role of these neuropeptides in epilepsy still is controversial. We analyzed the impact of AK and consequent activation of mesencephalic neurocircuits and the recruitment of forebrain limbic (LiR) sites on the hypothalamic-neurohypophysial system and expression of Avpr1a and Oxtr in these structures. At the end of the AK protocol, nine out of 18 WARs presented LiR. Increases in both plasma vasopressin and oxytocin levels were observed in WAR when compared to Wistar rats. These results were correlated with an increase in the expressions of heteronuclear (hn) and messenger (m) RNA for Oxt in the paraventricular nucleus (PVN) in WARs submitted to AK that presented LiR. In the paraventricular nucleus, the hnAvp and mAvp expressions increased in WARs with and without LiR, respectively. There were no significant differences in Avp and Oxt expression in supraoptic nuclei (SON). Also, there was a reduction in the Avpr1a expression in the central nucleus of the amygdala and frontal lobe in the WAR strain. In the inferior colliculus, Avpr1a expression was lower in WARs after AK, especially those without LiR. Our results indicate that both AK and LiR in WARs lead to changes in the hypothalamic-neurohypophysial system and its receptors, providing a new molecular basis to better understaind epilepsy.

Increased oxytocin release precedes hyponatremia after pituitary surgery.

PURPOSE: The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a well-known complication of transsphenoidal pituitary surgery, related to inappropriate secretion of arginine vasopressin (AVP). Its diagnosis is based on hyponatremia, with a peak of occurrence around day 7 after surgery and, to date, no early marker has been reported. In particular, copeptin levels are not predictive of hyponatremia in this case. Oxytocin (OXT) is secreted into the peripheral blood by axon terminals adjacent to those of AVP neurons in the posterior pituitary. Besides its role in childbirth and lactation, recent evidences suggested a role for OXT in sodium balance. The contribution of this hormone in the dysnatremias observed after pituitary surgery has however never been investigated. METHODS: We analyzed the urinary output of OXT in patients subjected to transsphenoidal pituitary surgery. RESULTS: While OXT excretion remained stable in patients who presented a normonatremic postoperative course, patients who were later diagnosed with SIADH-related hyponatremia presented with a significantly increased urinary secretion of OXT 4 days after surgery. CONCLUSION: Taken together, these results show for the first time that urinary OXT output remains normally stable after transsphenoidal pituitary surgery. OXT excretion however becomes abnormally high on or around 4 days after surgery in patients later developing hyponatremia, suggesting that this abnormal dynamics of OXT secretion might serve as an early marker for transsphenoidal surgery-related hyponatremia attributed to SIADH.

Clinical-Pathological, Immunohistochemical, and Genetic Characterization of a Series of Posterior Pituitary Tumors.

Posterior pituitary tumors are supposed to represent the morphological spectrum of a single entity. Herein, we report the clinical-pathological, immunohistochemical, and genetic features of 5 spindle cell oncocytomas (SCOs), 3 pituicytomas, and 1 granular cell tumor (GCT). SCOs had the highest local invasiveness and affected older subjects. The 3 histotypes differed in the content of spindle cells (predominant in pituicytoma and absent in GCT), presence of lymphocytic infiltrate (in SCO and GCT, but not in the pituicytoma) and EMA/GFAP staining (negative in GCT; EMA-positive/GFAP-negative in 4/5 SCO and GFAP-positive in 3/3 pituicytomas). Three SCOs and 1 pituicytoma analyzed with next-generation sequencing had no mutations in 409 genes. However, 1 SCO had previously unreported homozygous deletion of CDKN2A/B and another of SMARCA4, SMARCB1, and NF2. All 3 SCOs had loss of heterozygosity of chromosome 1p, while the pituicytoma had chromosome 19 homozygous loss and chromosomes 10, 13q, and 18q loss of heterozygosity. Since 1p and 13q losses were previously reported in 1 pituicytoma and 1 SCO, respectively, our data demonstrate that posterior pituitary tumors share common genetic alterations. The possibility that posterior pituitary tumors are SMARCA4/SMARCB1-deficient should be kept in mind in the differential diagnosis toward other entities.

Differential distribution and potential regulatory roles of estrogen receptor 2a and 2b in the pituitary of ricefield eel Monopterus albus.

Estrogens play important regulatory roles in the pituitary of vertebrates. Two forms of estrogen receptor 2 (Esr2), namely Esr2a and Esr2b, are identified in teleosts, but their differential roles remain to be fully elucidated. In the present study, expression and potential functional roles of Esr2a and Esr2b were characterized in ricefield eels. esr2a and esr2b mRNA were broadly distributed in tissues, with high levels observed in the brain, pituitary, and gonads. In order to examine the cellular localization of Esr2a and Esr2b in the pituitary, specific antisera against ricefield eel Esr2a and Esr2b were generated, respectively. Interestingly, immunohistochemistry and Western blot analysis revealed that Esr2a and Esr2b were differentially distributed in the pituitary, with the former localized to the adenohypophysis while the latter to the neurohypophysis. Dual fluorescent immunostaining showed that immunoreactive Esr2a was present in Gh and Prl cells, but not in Lh and Fsh cells. Estradiol (E2) stimulated lhb and prl gene expression in dispersed pituitary cells of intersexual ricefield eels, but had no effects on gh, fshb, and gnrhr2 gene expression and Gh release. Results of the present study are helpful for further understanding the roles and mechanisms of estrogen signals in the pituitary.

Basophilic invasion in the neurohypophysis is increased in patients with Alzheimer's disease.

PURPOSE: The prevalence of basophilic invasion (BI) and degenerative changes in the neurohypophysis of humans with neurodegenerative disease is not established. MATERIALS AND METHODS: We evaluated 122 pituitary glands reviewed at autopsy including 45 with Alzheimer's disease (AD) Braak and Braak stage V or VI, 18 with Lewy body disease (LBD), and 59 age-matched controls for BI. In addition, pituitary glands from 51 patients including 25 patients with AD and 18 aged-matched controls were studied with a periodic acid Schiff (PAS) stain and immunohistochemistry with a polyclonal antibody to nestin. Samples were graded as negative (0) or positive (1). RESULTS: BI was seen in 35 of 45 patients with AD (0.78 ± 0.06 mean and SE: 78%) and was significantly higher than 30 of 59 controls (0.51 ± 0.07; 51%) (p = 0.0236). BI was seen in 7 of 18 patients with LBD (0.39 ± 0.12; 39%) compared to controls (p = 0.387). BI was also significantly higher in AD compared to LBD (p = 0.0001). Nestin immunoreactivity was detected in the neurohypophysis of all patients. Definite nestin was not found in BI but was seen in Herring body-like structures, in pituicytes and axons. Phospho-τ-immunoreactive Herring bodies were seen in 65% with AD but phospho-τ-immunoreactive neurofibrillary tangles were not found. CONCLUSION: BI is increased in AD compared to controls or LBD but not associated with nestin immunoreactivity. The significance and role of BI as a marker for AD warrants additional study.

Sudden death in epilepsy and ectopic neurohypophysis in Joubert syndrome 23 diagnosed using SNVs/indels and structural variants pipelines on WGS data: a case report.

BACKGROUND: Joubert syndrome (JBTS) is a genetically heterogeneous group of neurodevelopmental syndromes caused by primary cilia dysfunction. Usually the neurological presentation starts with abnormal neonatal breathing followed by muscular hypotonia, psychomotor delay, and cerebellar ataxia. Cerebral MRI shows mid- and hindbrain anomalies including the molar tooth sign. We report a male patient with atypical presentation of Joubert syndrome type 23, thus expanding the phenotype. CASE PRESENTATION: Clinical features were consistent with JBTS already from infancy, yet the syndrome was not suspected before cerebral MRI later in childhood showed the characteristic molar tooth sign and ectopic neurohypophysis. From age 11 years seizures developed and after few years became increasingly difficult to treat, also related to inadequate compliance to therapy. He died at 23 years of sudden unexpected death in epilepsy (SUDEP). The genetic diagnosis remained elusive for many years, despite extensive genetic testing. We reached the genetic diagnosis by performing whole genome sequencing of the family trio and analyzing the data with the combination of one analysis pipeline for single nucleotide variants (SNVs)/indels and one for structural variants (SVs). This lead to the identification of the most common variant detected in patients with JBTS23 (OMIM# 616490), rs534542684, in compound heterozygosity with a 8.3 kb deletion in KIAA0586, not previously reported. CONCLUSIONS: We describe for the first time ectopic neurohypophysis and SUDEP in JBTS23, expanding the phenotype of this condition and raising the attention on the possible severity of the epilepsy in this disease. We also highlight the diagnostic power of WGS, which efficiently detects SNVs/indels and in addition allows the identification of SVs.

Impaired experience-dependent maternal care in presynaptic active zone protein CAST-deficient dams.

Although sociological studies affirm the importance of parental care in the survival of offspring, maltreatment-including child neglect-remains prevalent in many countries. While child neglect is well known to affect child development, the causes of maternal neglect are poorly understood. Here, we found that female mice with a deletion mutation of CAST (a presynaptic release-machinery protein) showed significantly reduced weaning rate when primiparous and a recovered rate when multiparous. Indeed, when nurturing, primiparous and nulliparous CAST knock out (KO) mice exhibited less crouching time than control mice and moved greater distances. Contrary to expectations, plasma oxytocin (OXT) was not significantly reduced in CAST KO mice even though terminals of magnocellular neurons in the posterior pituitary expressed CAST. We further found that compared with control mice, CAST KO mice drank significantly less water when nurturing and had a greater preference for sucrose during pregnancy. We suggest that deficiency in presynaptic release-machinery protein impairs the facilitation of some maternal behaviours, which can be compensated for by experience and learning.

Single-Cell Molecular and Cellular Architecture of the Mouse Neurohypophysis.

The neurohypophysis (NH), located at the posterior lobe of the pituitary, is a major neuroendocrine tissue, which mediates osmotic balance, blood pressure, reproduction, and lactation by means of releasing the neurohormones oxytocin (OXT) and arginine-vasopressin (AVP) from the brain into the peripheral blood circulation. The major cellular components of the NH are hypothalamic axonal termini, fenestrated endothelia and pituicytes, the resident astroglia. However, despite the physiological importance of the NH, the exact molecular signature defining neurohypophyseal cell types and in particular the pituicytes, remains unclear. Using single-cell RNA sequencing (scRNA-Seq), we captured seven distinct cell types in the NH and intermediate lobe (IL) of adult male mouse. We revealed novel pituicyte markers showing higher specificity than previously reported. Bioinformatics analysis demonstrated that pituicyte is an astrocytic cell type whose transcriptome resembles that of tanycyte. Single molecule in situ hybridization revealed spatial organization of the major cell types implying intercellular communications. We present a comprehensive molecular and cellular characterization of neurohypophyseal cell types serving as a valuable resource for further functional research.

Neuropathic Pain Up-Regulates Hypothalamo-Neurohypophysial and Hypothalamo-Spinal Oxytocinergic Pathways in Oxytocin-Monomeric Red Fluorescent Protein 1 Transgenic Rat.

Despite the high incidence of neuropathic pain, its mechanism remains unclear. Oxytocin (OXT) is an established endogenous polypeptide produced in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus. OXT, which is synthesized by OXT neurons in the SON and the magnocellular part of the PVN (mPVN), is delivered into the posterior pituitary (PP), then released into the systemic blood circulation. Meanwhile, OXT-containing neurosecretory cells in the parvocellular part of the PVN (pPVN) are directly projected to the spinal cord and are associated with sensory modulation. In this study, the OXT system in the hypothalamo-neurohypophysial and hypothalamo-spinal pathway was surveyed using a rat neuropathic pain model induced by partial sciatic nerve ligation (PSL). In the present study, we used transgenic rats expressing an OXT-monomeric red fluorescent protein 1 (mRFP1) fusion gene. In a neuropathic pain model, mechanical allodynia was observed, and glial cell activation was also confirmed via immunohistochemistry. In this neuropathic pain model, a significant increase in the OXT-mRFP1 expression was observed in the PP, the SON, mPVN, and pPVN. Furthermore, OXT-mRFP1 granules with positive fluorescent reaction were remarkably increased in laminae I and II of the ipsilateral dorsal horn. Although the plasma concentrations of OXT did not significantly change, a significant increase of the mRNA levels of OXT and mRFP1 in the SON, mPVN, and pPVN were observed. These results suggest that neuropathic pain induced by PSL upregulates hypothalamic OXT synthesis and transportation to the OXTergic axon terminals in the PP and spinal cord.

Posterior pituitary dysfunction following traumatic brain injury: review.

Neurohypophysial dysfunction is common in the first days following traumatic brain injury (TBI), manifesting as dysnatremia in approximately 1 in 4 patients. Both hyponatremia and hypernatremia can impair recovery from TBI and in the case of hypernatremia, there is a significant association with excess mortality. Hyponatremia secondary to syndrome of inappropriate antidiuretic hormone secretion (SIAD) is the commonest electrolyte disturbance following TBI. Acute adrenocorticotropic hormone (ACTH)/cortisol deficiency occurs in 10-15% of TBI patients and can present with a biochemical picture identical to SIAD. For this reason, exclusion of glucocorticoid deficiency is of particular importance in post-TBI SIAD. Cerebral salt wasting is a rare cause of hyponatremia following TBI. Hyponatremia predisposes to seizures, reduced consciousness, and prolonged hospital stay. Diabetes insipidus (DI) occurs in 20% of cases following TBI; where diminished consciousness is present, appropriate fluid replacement of renal water losses is occasionally inadequate, leading to hypernatremia. Hypernatremia is strongly predictive of mortality following TBI. Most cases of DI are transient, but persistent DI is also predictive of mortality, irrespective of plasma sodium concentration. Persistent DI may herald rising intracranial pressure due to coning. True adipsic DI is rare following TBI, but patients are vulnerable to severe hypernatremic dehydration, exacerbation of neurologic deficits and hypothalamic complications, therefore clinicians should be aware of this possible variant of DI.

Diversity of central oxytocinergic projections.

Localization and distribution of hypothalamic neurons expressing the nonapeptide oxytocin has been extensively studied. Their projections to the neurohypophyseal system release oxytocin into the systemic circulation thus controlling endocrine events associated with reproduction in males and females. Oxytocinergic neurons seem to be confined to the ventral hypothalamus in all mammals. Groups of such cells located outside the supraoptic and the paraventricular nuclei are summarized as "accessory neurons." Although evolutionary probably associated with the classical magocellular nuclei, accessory oxytocin neurons seem to consist of rather heterogenous groups: Periventricular oxytocin neurons may gain contact to the third ventricle to secrete the peptide into the cerebrospinal fluid. Perivascular neurons may be involved in control of cerebral blood flow. They may also gain access to the portal circulation of the anterior pituitary lobe. Central projections of oxytocinergic neurons extend to portions of the limbic system, to the mesencephalon and to the brain stem. Such projections have been associated with control of behaviors, central stress response as well as motor and vegetative functions. Activity of the different oxytocinergic systems seems to be malleable to functional status, strongly influenced by systemic levels of steroid hormones.

Pituicyte Cues Regulate the Development of Permeable Neuro-Vascular Interfaces.

The hypothalamo-neurohypophyseal system (HNS) regulates homeostasis through the passage of neurohormones and blood-borne proteins via permeable blood capillaries that lack the blood-brain barrier (BBB). Why neurohypophyseal capillaries become permeable while the neighboring vasculature of the brain forms BBB remains unclear. We show that pituicytes, the resident astroglial cells of the neurohypophysis, express genes that are associated with BBB breakdown during neuroinflammation. Pituicyte-enriched factors provide a local microenvironment that instructs a permeable neurovascular conduit. Thus, genetic and pharmacological perturbations of Vegfa and Tgfß3 affected HNS vascular morphogenesis and permeability and impaired the expression of the fenestral marker plvap. The anti-inflammatory agent dexamethasone decreased HNS permeability and downregulated the pituicyte-specific cyp26b gene, encoding a retinoic acid catabolic enzyme. Inhibition of Cyp26b activity led to upregulation of tight junction protein Claudin-5 and decreased permeability. We conclude that pituicyte-derived factors regulate the "decision" of endothelial cells to adopt a permeable endothelial fate instead of forming a BBB.

Vasopressin and oxytocin in sensory neurones: expression, exocytotic release and regulation by lactation.

The neurohormones arginine-vasopressin (AVP) and oxytocin (OT) synthesised in supraoptic and paraventricular nuclei of neurohypophysis regulate lactation, systemic water homeostasis and nociception. Using transgenic rats expressing AVP and OT tagged with fluorescent proteins we demonstrate that both neurohormones are expressed in sensory neurones both in vitro, in primary cultures, and in situ, in the intact ganglia; this expression was further confirmed with immunocytochemistry. Both neurohormones were expressed in nociceptive neurones immunopositive to transient receptor potential vannilloid 1 (TRPV1) channel antibodies. The AVP and OT-expressing DRG neurones responded to AVP, OT, 50 mM K+ and capsaicin with [Ca2+]i transients; responses to AVP and OT were specifically blocked by the antagonists of V1 AVP and OT receptors. Probing the extracellular incubation saline with ELISA revealed AVP and OT secretion from isolated DRGs; this secretion was inhibited by tetanus toxin (TeNT) indicating the role for vesicular release. Expression of OT, but not AVP in DRG neurones significantly increased during lactation. Together, the results indicate novel physiological roles (possibly related to nociception and mood regulation) of AVP and OT in the sensory neurones.

The posterior pituitary expresses the serotonin receptor 2C.

The serotonin receptor 2C (5HT2C) is an important drug target to treat obesity and depression. Its pre-mRNA undergoes alternative splicing, encoding a short RNA1 isoform that is localized intracellularly and a full-length isoform (RNA2) that can reach the cell membrane. These splicing isoforms are deregulated in Prader-Willi syndrome (PWS), due to the loss of a trans-acting regulatory RNA, SNORD115. Here we show that the 5HT2C mRNA is expressed in the posterior pituitary, suggesting that 5HT2C mRNA is generated in the hypothalamus and subsequently conveyed by axonal transport. In the pituitary, the ratio of 5HT2C isoforms is regulated by feeding, and can be manipulated using a splice-site changing oligonucleotide injected into the blood. The pituitary expression of the 5HT2C mRNA may constitute a previously unknown mechanism whereby serotonin in the circulation or drugs targeting the 5HT2C might induce side-effects. Finally, the deregulation of 5HT2C splicing isoforms in PWS could contribute to the known hormonal imbalances.

The effects of aging on biosynthetic processes in the rat hypothalamic osmoregulatory neuroendocrine system.

Elderly people exhibit a diminished capacity to cope with osmotic challenges such as dehydration. We have undertaken a detailed molecular analysis of arginine vasopressin (AVP) biosynthetic processes in the supraoptic nucleus (SON) of the hypothalamus and secretory activity in the posterior pituitary of adult (3 months) and aged (18 months) rats, to provide a comprehensive analysis of age-associated changes to the AVP system. By matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis, we identified differences in pituitary peptides, including AVP, in adult and aged rats under both basal and dehydrated states. In the SON, increased Avp gene transcription, coincided with reduced Avp promoter methylation in aged rats. Based on transcriptome data, we have previously characterized a number of novel dehydration-induced regulatory factors involved in the response of the SON to osmotic cues. We found that some of these increase in expression with age, while dehydration-induced expression of these genes in the SON was attenuated in aged rats. In summary, we show that aging alters the rat AVP system at the genome, transcriptome, and peptidome levels. These alterations however did not affect circulating levels of AVP in basal or dehydrated states.