Alleviation of Cerebral Infarction of Rats With Middle Cerebral Artery Occlusion by Inhibition of Aquaporin 4 in the Supraoptic Nucleus.

In ischemic stroke, vasopressin hypersecretion is a critical factor of cerebral swelling and brain injury. To clarify neural mechanisms underlying ischemic stroke-evoked vasopressin hypersecretion, we observed the effect of unilateral permanent middle cerebral artery occlusion (MCAO) in rats on astrocytic plasticity and vasopressin neuronal activity in the supraoptic nucleus (SON) as well as their associated cerebral injuries. MCAO for 8 hr caused cerebral infarction in the MCAO side where water contents also increased. Immunohistochemical examination revealed that the percentage of phosphorylated extracellular signal-regulated protein kinase 1/2 (pERK1/2)-positive vasopressin neurons in the SON of MCAO side was significantly higher than that in non-MCAO side and in sham group. In the cortex, pERK1/2 and aquaporin 4 expressions increased significantly in the infarction area, while glial fibrillary acidic protein (GFAP) reduced significantly compared with the noninfarction side in brain cortex. Microinjection of N-(1,3,4-Thiadiazolyl)nicotinamide-020 [TGN-020, a specific blocker of aquaporin 4] into the SON blocked MCAO-evoked increases in pERK1/2 in the SON as well as the reduction of GFAP and the increase in pERK1/2 and aquaporin 4 in the infarction area of the cortex. Finally, oxygen and glucose deprivation reduced GFAP expression and the colocalization and molecular association of GFAP with aquaporin 4 in the SON in brain slices. These effects were blocked by TGN-020 and/or phloretin, a blocker of astrocytic volume-regulated anion channels. These findings indicate that blocking aquaporin 4 in the SON may reduce the activation of vasopressin neurons and brain injuries elicited by vasopressin during ischemic stroke.

Brain-Derived Neurotrophic Factor and Supraoptic Vasopressin Neurons in Hyponatremia.

Hyponatremia due to elevated arginine vasopressin (AVP) secretion increases mortality in liver failure patients. The mechanisms causing dysregulation of AVP secretion are unknown. Our hypothesis is that inappropriate AVP release associated with liver failure is due to increased brain-derived neurotrophic factor (BDNF) in the supraoptic nucleus (SON). BDNF diminishes GABAA inhibition in SON AVP neurons by increasing intracellular chloride through tyrosine receptor kinase B (TrkB) activation and downregulation of K+/Cl- cotransporter 2 (KCC2). This loss of inhibition could increase AVP secretion. This hypothesis was tested using shRNA against BDNF (shBDNF) in the SON in bile duct ligated (BDL) male rats. All BDL rats had significantly increased liver weight (p < 0.05; 6-9) compared to shams. BDL rats with control -shRNA injections (BDL scrambled [SCR]) developed hyponatremia with increased plasma AVP and copeptin (CPP; all p < 0.05; 6-9) compared to sham groups. This is the first study to show that phosphorylation of TrkB is significantly increased along with significant decrease in phosphorylation of KCC2 in BDL SCR rats compared to the sham rats (p < 0.05;6-8). Knockdown of BDNF in the SON of BDL rats (BDL shBDNF) significantly increased plasma osmolality and hematocrit compared to BDL SCR rats (p < 0.05; 6-9). The BDL shBDNF rats had significant (p < 0.05; 6-9) decreases in plasma AVP and CPP concentration compared to BDL SCR rats. The BDNF knockdown also significantly blocked the increase in TrkB phosphorylation and decrease in KCC2 phosphorylation (p < 0.05; 6-8). The results indicate that BDNF produced in the SON contributes to increased AVP secretion and hyponatremia during liver failure.

Excitatory GABAergic Action and Increased Vasopressin Synthesis in Hypothalamic Magnocellular Neurosecretory Cells Underlie the High Plasma Level of Vasopressin in Diabetic Rats.

Diabetes mellitus (DM) is associated with increased plasma levels of arginine-vasopressin (AVP), which may aggravate hyperglycemia and nephropathy. However, the mechanisms by which DM may cause the increased AVP levels are not known. Electrophysiological recordings in supraoptic nucleus (SON) slices from streptozotocin (STZ)-induced DM rats and vehicle-treated control rats revealed that γ-aminobutyric acid (GABA) functions generally as an excitatory neurotransmitter in the AVP neurons of STZ rats, whereas it usually evokes inhibitory responses in the cells of control animals. Furthermore, Western blotting analyses of Cl- transporters in the SON tissues indicated that Na+-K+-2Cl- cotransporter isotype 1 (a Cl- importer) was upregulated and K+-Cl- cotransporter isotype 2 (KCC2; a Cl- extruder) was downregulated in STZ rats. Treatment with CLP290 (a KCC2 activator) significantly lowered blood AVP and glucose levels in STZ rats. Last, investigation that used rats expressing an AVP-enhanced green fluorescent protein fusion gene showed that AVP synthesis in AVP neurons was much more intense in STZ rats than in control rats. We conclude that altered Cl- homeostasis that makes GABA excitatory and enhanced AVP synthesis are important changes in AVP neurons that would increase AVP secretion in DM. Our data suggest that Cl- transporters in AVP neurons are potential targets of antidiabetes treatments.

The protective effects of electro-acupuncture in thoracic surgery on trauma stressed rats involve the rostral ventrolateral medulla and supraoptic nucleus.

The present study was designed to explore whether the rostral ventrolateral medulla (RVLM) and supraoptic nucleus (SON) were involved in the protective effects of electro-acupuncture (EA) in thoracic surgery on trauma-stressed rats. The rats were randomly divided into a non-stressed group (Control), surgical trauma-stressed group (Trauma), and Neiguan EA applied on the surgical trauma-stressed group (Trauma+EA-PC 6). RVLM neuron discharge was observed by using an in vivo electrophysiological method, and micro-dialysis combining high-performance liquid chromatography with fluorometric detection (HPLC-FD) was used to assess expression of amino acids in the RVLM. Immunohistochemical methods were used to assess c-Fos expression in SON neurons. The trauma of surgical stress was shown to dramatically increase the discharge frequency of RVLM neurons and promote the release of glutamate and taurine in the RVLM. The expression of c-Fos was also significantly increased in the SON of traumatized rats. EA application at Neiguan acupoints significantly suppressed trauma-induced increase of discharge frequency of the RVLM neurons, almost completely suppressed the trauma-induced increase of glutamate release but only very slightly reduced the trauma-enhanced taurine release, and inhibited the increase of c-Fos expression in these SON neurons of traumatized rats. These results indicate that Neiguan EA may improve cardiac function by modulating neurons in the RVLM and the SON in surgically traumatized rats. The taurine-mediated negative feedback may be involved in the protective effect of EA on cardiac function.

Perinatal exposure to organohalogen pollutants decreases vasopressin content and its mRNA expression in magnocellular neuroendocrine cells activated by osmotic stress in adult rats.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that produce neurotoxicity and neuroendocrine disruption. They affect the vasopressinergic system but their disruptive mechanisms are not well understood. Our group reported that rats perinatally exposed to Aroclor-1254 (A1254) and DE-71 (commercial mixtures of PCBs and PBDEs) decrease somatodendritic vasopressin (AVP) release while increasing plasma AVP responses to osmotic activation, potentially emptying AVP reserves required for body-water balance. The aim of this research was to evaluate the effects of perinatal exposure to A1254 or DE-71 (30mgkg/day) on AVP transcription and protein content in the paraventricular and supraoptic hypothalamic nuclei, of male and female rats, by in situ hybridization and immunohistochemistry. cFOS mRNA expression was evaluated in order to determine neuroendocrine cells activation due to osmotic stimulation. Animal groups were: vehicle (control); exposed to either A1254 or DE-71; both, control and exposed, subjected to osmotic challenge. The results confirmed a physiological increase in AVP-immunoreactivity (AVP-IR) and gene expression in response to osmotic challenge as reported elsewhere. In contrast, the exposed groups did not show this response to osmotic activation, they showed significant reduction in AVP-IR neurons, and AVP mRNA expression as compared to the hyperosmotic controls. cFOS mRNA expression increased in A1254 dehydrated groups, suggesting that the AVP-IR decrease was not due to a lack of the response to the osmotic activation. Therefore, A1254 may interfere with the activation of AVP mRNA transcript levels and protein, causing a central dysfunction of vasopressinergic system.

Age-Related (Aged vs. Adult) Comparison of the Effect of Two Mild Stressors on the Nerve Growth Factor (NGF) in the Rat Hypothalamic Supraoptic Nucleus (SON) - Immunohistochemical Study.

The ontogenetic period of life and stress can have different effects on the nerve growth factor (NGF) in the hypothalamus. The aim of our study was to investigate the influence of two mild stressors, acute and chronic exposure to forced swim (FS) or high-light open field (HL-OF), on neurons containing NGF. Immunofluorescence staining was used to reveal the density of NGF-immunoreactive (ir) cells in the hypothalamic supraoptic nucleus (SON) in adult (postnatal day 90; P90) and aged (P720) rats. The P90 and P720 rats that were subjected to acute and chronic FS showed no differences in the density of NGF-ir neurons in the SON compared with nonstressed rats. However, a significant increase in NGF-ir cells was noted after acute but not after chronic HL-OF only in P90 rats. What is more, there were no age-related (P90 vs. P720) changes in the density of NGF-ir neurons in non-stressed and FS- or HL-OF-stressed rats. Our results indicate that acute HL-OF was the only factor inducing changes in the density of NGF-ir neurons in the SON of adult rats. This could be related to the neuroprotective role of NGF-ir cells in response to acute HL-OF. The absence of age-dependent changes in the density of NGF-ir neurons may indicate that the ageing processes in SON do not generate changes in the NGF immunoreactivity of its neurons.

Oestradiol effects on neuroendocrine responses induced by water deprivation in rats.

Water deprivation (WD) induces changes in plasma volume and osmolality, which in turn activate several responses, including thirst, the activation of the renin-angiotensin system (RAS) and vasopressin (AVP) and oxytocin (OT) secretion. These systems seem to be influenced by oestradiol, as evidenced by the expression of its receptor in brain areas that control fluid balance. Thus, we investigated the effects of oestradiol treatment on behavioural and neuroendocrine changes of ovariectomized rats in response to WD. We observed that in response to WD, oestradiol treatment attenuated water intake, plasma osmolality and haematocrit but did not change urinary volume or osmolality. Moreover, oestradiol potentiated WD-induced AVP secretion, but did not alter the plasma OT or angiotensin II (Ang II) concentrations. Immunohistochemical data showed that oestradiol potentiated vasopressinergic neuronal activation in the lateral magnocellular PVN (PaLM) and supraoptic (SON) nuclei but did not induce further changes in Fos expression in the median preoptic nucleus (MnPO) or subfornical organ (SFO) or in oxytocinergic neuronal activation in the SON and PVN of WD rats. Regarding mRNA expression, oestradiol increased OT mRNA expression in the SON and PVN under basal conditions and after WD, but did not induce additional changes in the mRNA expression for AVP in the SON or PVN. It also did not affect the mRNA expression of RAS components in the PVN. In conclusion, our results show that oestradiol acts mainly on the vasopressinergic system in response to WD, potentiating vasopressinergic neuronal activation and AVP secretion without altering AVP mRNA expression.

A single prolonged stress paradigm produces enduring impairments in social bonding in monogamous prairie voles.

Traumatic events such as natural disasters, violent crimes, tragic accidents, and war, can have devastating impacts on social relationships, including marital partnerships. We developed a single prolonged stress (SPS) paradigm, which consisted of restraint, forced swimming, and ether anesthesia, to establish an animal model relevant to post-traumatic stress disorder. We applied a SPS paradigm to a monogamous rodent, the prairie vole (Microtus ochrogaster) in order to determine whether a traumatic event affects the establishment of pair bonds. We did not detect effects of the SPS treatment on anhedonic or anxiety-like behavior. Sham-treated male voles huddled with their partner females, following a 6day cohabitation, for a longer duration than with a novel female, indicative of a pair bond. In contrast, SPS-treated voles indiscriminately huddled with the novel and partner females. Interestingly, the impairment of pair bonding was rescued by oral administration of paroxetine, a selective serotonin reuptake inhibitor (SSRI), after the SPS treatment. Immunohistochemical analyses revealed that oxytocin immunoreactivity (IR) was significantly decreased in the supraoptic nucleus (SON), but not in the paraventricular nucleus (PVN), 7days after SPS treatment, and recovered 14days after SPS treatment. After the presentation of a partner female, oxytocin neurons labeled with Fos IR was significantly increased in SPS-treated voles compared with sham-treated voles regardless of paroxetine administration. Our results suggest that traumatic events disturb the formation of pair bond possibly through an interaction with the serotonergic system, and that SSRIs are candidates for the treatment of social problems caused by traumatic events. Further, a vole SPS model may be useful for understanding mechanisms underlying the impairment of social bonding by traumatic events.

The human neurosecretory neurones under perinatal hypoxia: a quantitative immunohistochemical study of the supraoptic nucleus in autopsy material.

In the rat, experimental manipulations that cause activation of the magnocellular neurosecretory neurones result in the synthesis, in addition to vasopressin (AVP) and oxytocin (OXY), of other neurotransmitters or peptides, including tyrosine hydroxylase (TH), the first and rate limiting enzyme for catecholamine biosynthesis. In the human neonate, our previous study showed that TH was selectively increased in AVP neurones of subjects that died from prolonged perinatal hypoxia. The purpose of the present study was to quantitatively investigate the expression of TH, AVP, OXY and neurophysin in magnocellular neurones of the human neonate in relation to the severity/duration of perinatal hypoxia, as estimated by neuropathological criteria. Autopsy was performed after obtaining parental written consent for diagnostic and research purposes. The intensity of the immunohistochemical reactions and the cellular/nuclear size were measured in the dorsolateral supraoptic nucleus using a computerised image analysis system. We showed that prolonged perinatal hypoxia resulted in the activation of the magnocellular neuroendocrine neurones of the human neonate, as indicated by their increased neuronal and nuclear size. OXY neurones appeared larger than the AVP ones at birth, possibly indicating an active role of foetal OXY during labour or even earlier. The gradual increase in the duration of the insult resulted in the reduction of intracellular AVP content, in parallel with a dramatic increase in the expression of TH, indicating a functional interaction of these peptides under neuronal activation. Ιsolated evidence in our series, obtained from an infant of a diabetic mother, raises the probability that in the case of hyperglycaemia the above pathogenetic mechanisms are diversified.

Melanocortin 4 receptor distribution in the human hypothalamus.

OBJECTIVE: The melanocortin 4 receptor (MC4R) is an essential regulator of energy homeostasis and metabolism, and MC4R mutations represent the most prevalent monogenetic cause of obesity in humans known to date. Hypothalamic MC4Rs in rodents are well characterized in neuroanatomical and functional terms, but their expression pattern in the human hypothalamus is unknown. DESIGN AND METHODS: To determine the topographic distribution and identity of cells expressing MC4R mRNA in the human hypothalamus, locked nucleic acid in situ hybridization was performed on nine human postmortem hypothalami. In addition, co-expression of MC4R with glial fibrillary acidic protein (GFAP), vasopressin/oxytocin (AVP/OXT), corticotropin-releasing hormone (CRH), neuropeptide Y (NPY), agouti-related protein (AgRP), and α-melanocyte stimulating hormone (α-MSH) was examined. RESULTS: Most intense MC4R mRNA expression was present in the paraventricular nucleus (PVN), the supraoptic nucleus (SON), and the nucleus basalis of Meynert. Most MC4R-positive cells in the SON also expressed AVP/OXT. Co-expression with AVP/OXT in the PVN was less abundant. We did not observe co-expression of MC4R mRNA and GFAP, CRH, NPY, AgRP, or α-MSH. However, fiber-like staining of NPY, AgRP, and α-MSH was found adjacent to MC4R-positive cells in the PVN. CONCLUSION: Expression of MC4R mRNA in the human hypothalamus is widespread and in close approximation to endogenous MC4R binding partners AgRP and α-MSH.

Involvement of brain ANG II in acute sodium depletion induced salty taste changes.

Many investigations have been devoted to determining the role of angiotensin II (ANG II) and aldosterone (ALD) in sodium-depletion-induced sodium appetite, but few were focused on the mechanisms mediating the salty taste changes accompanied with sodium depletion. To further elucidate the mechanism of renin-angiotensin-aldosterone system (RAAS) action in mediating sodium intake behavior and accompanied salty taste changes, the present study examined the salty taste function changes accompanied with sodium depletion induced by furosemide (Furo) combined with different doses of angiotensin converting enzyme (ACE) inhibitor, captopril (Cap). Both the peripheral and central RAAS activity and the nuclei Fos immunoreactivity (Fos-ir) expression in the forebrain area were investigated. Results showed that sodium depletion induced by Furo+low-Cap increased taste preference for hypertonic NaCl solution with amplified brain action of ANG II but without peripheral action, while Furosemide combined with a high dose of captopril can partially inhibit the formation of brain ANG II, with parallel decreased effects on salty taste changes. And the resulting elevating forebrain ANG II may activate a variety of brain areas including SFO, PVN, SON and OVLT in sodium depleted rats injected with Furo+low-Cap, which underlines salty taste function and sodium intake behavioral changes. Neurons in SFO and OVLT may be activated mainly by brain ANG II, while PVN and SON activation may not be completely ANG II dependent. These findings suggested that forebrain derived ANG II may play a critical role in the salty taste function changes accompanied with acute sodium depletion.

ΔFosB in the supraoptic nucleus contributes to hyponatremia in rats with cirrhosis.

Bile duct ligation (BDL), a model of hepatic cirrhosis, is associated with dilutional hyponatremia and inappropriate vasopressin release. ΔFosB staining was significantly increased in vasopressin and oxytocin magnocellular neurosecretory cells in the supraoptic nucleus (SON) of BDL rats. We tested the role of SON ΔFosB in fluid retention following BDL by injecting the SON (n = 10) with 400 nl of an adeno-associated virus (AAV) vector expressing ΔJunD (a dominant negative construct for ΔFosB) plus green fluorescent protein (GFP) (AAV-GFP-ΔJunD). Controls were either noninjected or injected with an AAV vector expressing only GFP. Three weeks after BDL or sham ligation surgery, rats were individually housed in metabolism cages for 1 wk. Average daily water intake was significantly elevated in all BDL rats compared with sham ligated controls. Average daily urine output was significantly greater in AAV-GFP-ΔJunD-treated BDL rats compared with all other groups. Daily average urine sodium concentration was significantly lower in AAV-GFP-ΔJunD-treated BDL rats than the other groups, although average daily sodium excretion was not different among the groups. SON expression of ΔJunD produced a diuresis in BDL rats that may be related to decreased circulating levels of vasopressin or oxytocin. These findings support the view that ΔFosB expression in SON magnocellular secretory cells contribute to dilutional hyponatremia in BDL rats.

Structural and neurochemical plasticity in both supraoptic and paraventricular nuclei of hypothalamus of a desert rodent Meriones shawi after a severe dehydration versus opposite treatment by rehydration: GFAP and vasopressin immunohistochemical study.

Various lines of evidence indicate that astrocytes can undergo morphological changes that modify their relationship to adjacent neurons in response to physiological stimulation such as dehydration. Supraoptic (SON) and paraventricular (PVN) nuclei of hypothalamus represent obvious examples of activity-dependent neuro-astrocytic plasticity. In the present study, Meriones shawi is used as an animal model. Moreover, GFAP and vasopressin expressions are used as indicators successively of astrocytes and neuronal activations. In order to evaluate the reversibility of the neuro-astrocytic plasticity in SON and PVN, prolonged episode of water deprivation followed by episode of rehydration were examined. Hence, we studied the immunoreactivity in various hydration states: water ad libitum, dehydration, and rehydration of animals. Our results showed that dehydration of Meriones induced a significant decrease of GFAP immunoreactivity accompanied by a significant increase of AVP immunoreactivity, the latter concerns both cell bodies and fibers in the same hypothalamic nuclei SON and PVN. Conversely, rehydration of animals shows a reversible phenomenon leading a return of vasopressin and GFAP immunoreactivities to the control level. These results show that both astrocytes and vasopressin neurons display a remarkable structural and physiological plasticity, allowing to M. shawi, a great ability to support the hostile conditions in dry environment.

Blockage of the afferent sensitive pathway prevents sympathetic atrophy and hemodynamic alterations in rat portal hypertension.

BACKGROUND AND AIMS: Portal hypertension causes arterial vasodilation and sympathetic atrophy in the splanchnic area. We aimed to demonstrate a relationship between hemodynamic alterations and sympathetic atrophy by investigating a pathway from sensitive afferent signals to mesenteric sympathetic ganglia. METHODS: Experiments were conducted in sham and portal vein ligated (PVL) adult and neonatal rats treated with vehicle or capsaicin. Hemodynamic parameters, and immunohistochemistry, immunofluorescence and Western blot of different tissues were analysed. RESULTS: cFos expression in the brain supraoptic nuclei was used to confirm abrogation of the afferent signal in capsaicin-treated PVL rats (effectively afferent blocked). Neonatal and adult PVL afferent blocked rats showed simultaneous prevention of hemodynamic alterations and sympathetic atrophy (measured by tyrosine hydroxylase expression in nerve structures of splanchnic vasculature). Not effectively afferent blocked rats showed none of these effects, behaving as PVL vehicle. All capsaicin treated animals presented loss of calcitonin gene-related peptide in superior mesenteric artery and ganglia, whereas neuronal nitric oxide synthase remained unaffected. Neuronal markers semaphorin-3A, nerve growth factor, its precursor and p75 neurotrophic receptor, were significantly over-expressed in the PVL sympathetic ganglia compared with sham, but not in effectively afferent blocked rats. Semaphorin-3A staining in mesenteric ganglia co-localized with vesicular acetylcholine transporter, but not with adrenergic, nitrergic and sensory axons, suggesting that semaphorin-3A might originate in preganglionic neurons. CONCLUSION: These results indicate that the nervous system has a central role in the genesis of the circulatory abnormalities of portal hypertension, and support that mesenteric sympathetic atrophy contributes to splanchnic arterial vasodilation.

Pathologic evaluation of the supraoptic and paraventricular nuclei in dementia.

BACKGROUND: The neuropeptide oxytocin, produced in the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus, is now understood to function as a neurotransmitter critical for various aspects of social cognition and pro-social behaviour. While patients with Frontotemporal dementia (FTD) display prominent and progressive deficits in such social behaviours, the integrity of these nuclei in FTD is not known. METHODS: We conducted a quantitative neuropathologic examination of the SON and PVN from patients with FTLD with TDP-43 proteinopathy, Alzheimer's disease, Lewy body disease and controls to determine whether significant pathologic changes or neuronal loss may contribute to the striking behavioural symptoms of FTD. RESULTS: Contrary to predictions, we found both nuclei to be free of significant pathologic change (TDP-43) in FTLD. In contrast, tau related pathology was found in the PVN in Alzheimer's disease, and alpha-synuclein pathology in the SON in patients with Lewy body dementia. CONCLUSIONS: These results indicate that the SON and PVN are resistant to FTLD TDP-43 pathology. They also support prior suggestions that the SON is resistant to Alzheimer's disease (AD) related pathology, and extend this to demonstrate SON susceptibility to alpha-synuclein pathology in patients with Lewy body dementia.

Central diabetes insipidus associated with impaired renal aquaporin-1 expression in mice lacking liver X receptor ß.

The present study demonstrates a key role for the oxysterol receptor liver X receptor ß (LXRß) in the etiology of diabetes insipidus (DI). Given free access to water, LXRß(-/-) but not LXRα(-/-) mice exhibited polyuria (abnormal daily excretion of highly diluted urine) and polydipsia (increased water intake), both features of diabetes insipidus. LXRß(-/-) mice responded to 24-h dehydration with a decreased urine volume and increased urine osmolality. To determine whether the DI was of central or nephrogenic origin, we examined the responsiveness of the kidney to arginine vasopressin (AVP). An i.p. injection of AVP to LXRß(-/-) mice revealed a partial kidney response: There was no effect on urine volume, but there was a significant increase of urine osmolality, suggesting that DI may be caused by a defect in central production of AVP. In the brain of WT mice LXRß was expressed in the nuclei of magnocellular neurons in the supraoptic and paraventricular nuclei of the hypothalamus. In LXRß(-/-) mice the expression of AVP was markedly decreased in the magnocellular neurons as well as in urine collected over a 24-h period. The persistent high urine volume after AVP administration was traced to a reduction in aquaporin-1 expression in the kidney of LXRß(-/-) mice. The LXR agonist (GW3965) in WT mice elicited an increase in urine osmolality, suggesting that LXRß is a key receptor in controlling water balance with targets in both the brain and kidney, and it could be a therapeutic target in disorders of water balance.

BiP mRNA expression is upregulated by dehydration in vasopressin neurons in the hypothalamus in mice.

The immunoglobulin heavy chain binding protein (BiP) is an endoplasmic reticulum (ER) chaperone that facilitates the proper folding of newly synthesized secretory and transmembrane proteins. Here we report that BiP mRNA was expressed in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus in wild-type mice under basal conditions. Dual in situ hybridization in the SON and PVN demonstrated that BiP mRNA was expressed in almost all the neurons of arginine vasopressin (AVP), an antidiuretic hormone. BiP mRNA expression levels were increased in proportion to AVP mRNA expression in the SON and PVN under dehydration. These data suggest that BiP is involved in the homeostasis of ER function in the AVP neurons in the SON and PVN.

Neuronal activity and axonal sprouting differentially regulate CNTF and CNTF receptor complex in the rat supraoptic nucleus.

We demonstrated previously that the hypothalamic supraoptic nucleus (SON) undergoes a robust axonal sprouting response following unilateral transection of the hypothalamo-neurohypophysial tract. Concomitant with this response is an increase in ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFRα) expression in the contralateral non-uninjured SON from which the axonal outgrowth occurs. While these findings suggest that CNTF may act as a growth factor in support of neuronal plasticity in the SON, it remained to be determined if the observed increase in neurotrophin expression was related to the sprouting response per se or more generally to the increased neurosecretory activity associated with the post-lesion response. Therefore we used immunocytochemistry and Western blot analysis to examine the expression of CNTF and the components of the CNTF receptor complex in sprouting versus osmotically-stimulated SON. Western blot analysis revealed a significant increase in CNTF, CNTFRα, and gp130, but not LIFRß, protein levels in the sprouting SON at 10days post lesion in the absence of neuronal loss. In contrast, osmotic stimulation of neurosecretory activity in the absence of injury resulted in a significant decrease in CNTF protein levels with no change in CNTFRα, gp130, or LIFRß protein levels. Immunocytochemical analysis further demonstrated gp130 localization on magnocellular neurons and astrocytes while the LIFRß receptor was found only on astrocytes in the SON. These results are consistent with the hypothesis that increased CNTF and CNTFR complex in the sprouting, metabolically active SON are related directly to the sprouting response and not the increase in neurosecretory activity.