Infusion Of Artificial Cerebrospinal Fluid Research Articles

Glutamate, Glutamine, GABA and Oxidative Products in the Pons Following Cortical Injury and Their Role in Motor Functional Recovery.

Brain injury leads to an excitatory phase followed by an inhibitory phase in the brain. The clinical sequelae caused by cerebral injury seem to be a response to remote functional inhibition of cerebral nuclei located far from the motor cortex but anatomically related to the injury site. It appears that such functional inhibition is mediated by an increase in lipid peroxidation (LP). To test this hypothesis, we report data from 80 rats that were allocated to the following groups: the sham group (n = 40), in which rats received an intracortical infusion of artificial cerebrospinal fluid (CSF); the injury group (n = 20), in which rats received CSF containing ferrous chloride (FeCl2, 50mM); and the recovery group (n = 20), in which rats were injured and allowed to recover. Beam-walking, sensorimotor and spontaneous motor activity tests were performed to evaluate motor performance after injury. Lipid fluorescent products (LFPs) were measured in the pons. The total pontine contents of glutamate (GLU), glutamine (GLN) and gamma-aminobutyric acid (GABA) were also measured. In injured rats, the motor deficits, LFPs and total GABA and GLN contents in the pons were increased, while the GLU level was decreased. In contrast, in recovering rats, none of the studied variables were significantly different from those in sham rats. Thus, motor impairment after cortical injury seems to be mediated by an inhibitory pontine response, and functional recovery may result from a pontine restoration of the GLN-GLU-GABA cycle, while LP may be a primary mechanism leading to remote pontine inhibition after cortical injury.

Modeling a potential SANS countermeasure by experimental manipulation of the translaminar pressure difference in mice

The spaceflight-associated neuro-ocular syndrome (SANS), which may present after prolonged exposure to microgravity, is thought to occur due to elevated intracranial pressure (ICP). Intracranial pressure interacts with intraocular pressure (IOP) to define the translaminar pressure difference (TLPD; IOP−ICP). We combined inducible models of ICP and IOP elevation in mice to interrogate the relationships among ICP, IOP, and TLPD, and to determine if IOP elevation could mitigate the phenotypes typically caused by elevated ICP and thereby serve as a countermeasure for SANS. Ten C57BL6J mice of both genders underwent experimental elevation of ICP via infusion of artificial cerebrospinal fluid into the subarachnoid space. One eye also underwent experimental elevation of IOP using the bead injection model. Intraocular pressure and ICP were monitored for 2 weeks. Optokinetic-based contrast sensitivity was measured at baseline and after 2 weeks, and post-mortem studies of optic nerve and retina anatomy were performed. Photopic contrast sensitivity was reduced more in IOP elevated than control eyes. Scotopic contrast sensitivity was reduced similarly in IOP elevated and control eyes. However, the pattern of scotopic vision loss was not uniform in IOP elevated eyes; there was minimal loss in eyes that most closely approximated the normal TLPD. Optic nerve axon loss, increased optic nerve disorganization, and retinal ganglion cell loss all occurred similarly between IOP elevated and control eyes. Elevation of IOP in eyes with elevated ICP may counterbalance some effects on vision loss but exacerbate others, suggesting complex relationships among IOP, ICP, and TLPD.

The effect of microinjection of CART 55-102 into the nucleus accumbens shell on morphine-induced conditioned place preference in rats: Involvement of the NMDA receptor

The addictive properties of opioids may be mediated to some extent by cocaine-and amphetamine-regulated transcript (CART) in the reward pathway. Moreover, some claims CART interacts with the glutamate system. Here, we evaluated whether intra-nucleus accumbens (NAc) shell infusions of CART induces Conditioned Place Preference (CPP) or Conditioned Place Aversion (CPA) and affects morphine reward. We also measured NR1 subunit expressions of the N-methyl-d-aspartate (NMDA) receptor in various parts of the reward pathway (NAc, prefrontal cortex and hippocampus) after conditioning tests. Animals with bilateral intra-NAc shell cannulas were place-conditioned with several doses of subcutaneous morphine prior to intra-NAc shell infusions of artificial cerebrospinal fluid (aCSF). Immunohistochemistry (IHC) showed a dose-dependent increase in the NR1 expression in all examined parts. When rats were conditioned with intra-NAc shell infusions of CART, CPP and CPA induced with 2.5 and 5 μg/side respectively and IHC showed NR1elevation with 2.5 and reduction with 5 μg/side in all areas. Sub-rewarding dose of CART administration (1.25 μg/side) prior to sub-rewarding dose of morphine (2.5 mg/kg) induced CPP and NR1 increased in all examined tissues in IHC. However, infusion of an aversive dose of CART (5 μg/side) prior to the rewarding dose of morphine (5 mg/kg) produced neither CPP nor CPA and NR1 in the NAc and hippocampus decreased significantly. It seems that the rewarding or aversive effects of intra-NAc shell CART and its facilitating or inhibiting effects on morphine reward are dose-dependent. Additionally, NMDA may be closely involved in the affective properties of opioids and CART in the reward pathway.

Protein kinase C isoforms as a target for manic-like behaviors and oxidative stress in a dopaminergic animal model of mania

Bipolar disorder (BD) is a chronic condition characterized by severe mood swings alternating between episodes of mania and depression. Evidence indicates that protein kinase C (PKC) and oxidative stress are important therapeutic targets for BD. However, what PKC isoforms that are precisely involved in this effect are unknown. Therefore, we evaluated the effects of the intracerebroventricular (ICV) injection of PKC inhibitors (lithium (Li), tamoxifen (TMX), PKCα inhibitor (iPKCα), PKCγ inhibitor (iPKCγ), and PKCε inhibitor (iPKCε)) on the manic-like behaviors and oxidative stress parameters (4-hydroxy-2-nonenal (4-HNE), 8-isoprostane (8-ISO), carbonyl groups, 3-nitrotyrosine (3-NT), glutathione peroxidase (GPx) and glutathione reductase (GR)) in the brains of rats submitted to the model of mania induced by methamphetamine (m-AMPH). Animals received a single ICV infusion of artificial cerebrospinal fluid, Li, TMX, iPKCα, iPKCγ or iPKCε followed by an intraperitoneal injection of saline or m-AMPH before the behavioral analysis (open-field task). Oxidative stress was evaluated in the striatum, frontal cortex, and hippocampus. ICV injection of Li, TMX or iPKCε blocked the m-AMPH-induced increase in the manic-like behaviors – crossings, rearings, visits to the center, sniffing, and grooming. ICV infusion of iPKCα triggered a decrease in these behaviors induced by m-AMPH. Besides, the iPKCε administration significantly prevented the oxidative damage to lipids and proteins, as well as disturbances in the activity of antioxidant enzymes induced by m-AMPH. The findings of the present study suggest that PKCε isoform is strongly implied in the antimanic and antioxidant effects of Li, TMX, and the other PKC inhibitors in the model of mania.

New Insight into the Mechanism of Mannitol Effects on Cerebrospinal Fluid Pressure Decrease and Craniospinal Fluid Redistribution

Intracranial hypertension, which often follows a severe brain injury, is usually treated with intravenous (i.v.) application of hyperosmolar solutions. The mechanism of intracranial cerebrospinal fluid (CSF) pressure decrease after such a treatment is still unclear. The aim of this article was to try to explain the mechanism of CSF pressure reduction after i.v. hyperosmolar mannitol bolus in regard to the changes in CSF volume. Two types of experiments were done on anesthetized cats before and after hyperosmolar mannitol application: ventriculo-cisternal perfusion at different perfusion rates, simultaneously measuring the perfusate outflow volume, and CSF pressure recording in the lateral ventricle before and during artificial CSF infusion. Mannitol application in the first group of cats significantly reduced collected prefusate volume during ventriculo-cisternal perfusion, and in the second group it prevented CSF pressure increase caused by artificial CSF infusion. Our results strongly suggest that the mechanism of hyperosmolar mannitol action after its i.v. application is based on osmotic fluid retrieval from interstitial and cerebrospinal compartments into the microvessels. This shift, without significant volume change inside the cranium, causes a predominant decrease of CSF volume in the spinal part of the system, which in turn leads to lowering of the CSF pressure. Spinal CSF volume decrease is enabled by the extensibility of the spinal dura, this way providing the possibility for CSF volume redistribution inside the CSF system, together with CSF pressure decrease. This mechanism of mannitol action is in accordance with the new hypothesis of CSF physiology.

Abstract P290: Central Angiotensin II and Interleukin-1©¬ Upregulate Brain Tumor Necrosis Factor-¥å Converting Enzyme in the Rat

Tumor necrosis factor-α (TNF-α) converting enzyme (TACE/ADAM17) proteolytically cleaves the extracellular domain of transmembrane TNF-α to release the soluble form of TNF-α that contributes to augmented sympathetic nerve activity in heart failure (HF) and hypertension (HTN). Our previous study indicated that TACE is upregulated in the subfornical organ (SFO) and hypothalamic paraventricular nucleus (PVN), two key cardiovascular and autonomic brain centers, in rats with ischemia-induced HF, and is associated with TNF-α –induced sympathetic excitation in that setting. However, the mechanisms regulating TACE activity in the brain remain a mystery. The present study sought to determine whether angiotensin II (ANG II) or interleukin-1β (IL-1β), which increase in SFO and PVN in HF, upregulate TACE expression. Urethane anesthetized male SD rats underwent a 4- hour intracerebroventricular (ICV) infusion of artificial cerebrospinal fluid (aCSF), ANG II (100 ng/hr) or IL-1β (50 ng/hr). Some rats were euthanized to collect SFO and PVN tissues to measure TACE mRNA and protein; others were transcardially perfused with 4% paraformaldehyde to immunostain for TACE in SFO and PVN. ICV infusion of ANG II (n=6) or IL-1β (n=6) significantly (*p<0.05) increased TACE mRNA level (fold change) in SFO (2.54 ± 0.24* and 2.36 ± 0.21*, respectively) and PVN (2.39* ± 0.25 and 2.23 ± 0.20*, respectively) compared with ICV aCSF infusion. Western blot analysis also revealed a significant increase in the TACE protein (normalized to β-actin) in ANG II or IL-1β infused rats in SFO (0.31±0.06* and 0.26±0.05* respectively) and PVN (0.27 ± 0.04*, 0.24 ± 0.03*, respectively) compared with ICV aCSF-infused rats (SFO: 0.12±0.05; PVN: 0.09±0.04). Confocal images exhibited that TACE-like immunoreactivity was markedly higher in all four subdivisions of PVN and in SFO in rats treated with ICV ANG II or IL-1β, compared with aCSF-infused rats. These data indicate that ANG II and IL-1β upregulate TACE expression in SFO and PVN, suggesting that activation of the renin-angiotensin system and augmented inflammation may upregulate TACE expression in the SFO and PVN in HF and HTN. TACE-mediated ectodomain shedding in SFO and PVN may contribute to ANG II- and cytokine-driven sympathoexcitation in HF and HTN.

Intracranial pressure and glaucoma: Is there a new therapeutic perspective on the horizon?

Primary open-angle glaucoma is one of the leading causes of irreversible blindness worldwide. Raised intraocular pressure is the most important modifiable risk factor and lowering it remains the mainstay therapeutic approach for slowing optic nerve damage and visual field progression in glaucoma patients. An intriguing finding of clinical retrospective and prospective studies is that intracranial pressure is lower in patients with glaucoma. Furthermore, in a recent study on monkeys subjected to an implantation of a lumboperitoneal cerebrospinal fluid shunt to lower intracranial pressure, chronic reduction in intracranial pressure was associated with the development of glaucoma-like pathology in half of the monkeys. In addition, a very recent study demonstrated that patients whose intracranial pressure has been lowered following ventriculoperitoneal shunt placement, as treatment for normal pressure hydrocephalus, have a significantly increased risk of developing normal-tension glaucoma. These findings suggest that a reduced intracranial pressure may play an important role in the pathogenesis of glaucoma. This may be due to an abnormally high pressure difference across the lamina cribrosa resulting in biomechanical changes of the optic nerve head and/or to a deficient clearance of toxic substances, particularly in the subarachnoid space of the optic nerve and/or in the ‘ocular glymphatic system’. The search for drugs or medical devices useful to ameliorate glaucoma by lowering the trans-lamina cribrosa pressure difference and/or by facilitating cerebrospinal fluid circulation may therefore be an important area for future research. In this article, we propose that infusion of artificial cerebrospinal fluid through an implantable pump into the intrathecal space surrounding the spinal cord could be a new promising strategy for the treatment of glaucoma. Although the implantation of such a cerebrospinal fluid pump is a relatively invasive intervention, it seems worthwhile to make every effort to identify new therapies for patients who suffer from this devastating disease, especially given the significant number of patients for whom non-invasive treatment options are ineffective.

MP81-01 CENTRAL TUMOR NECROSIS FACTOR-ALPHA BLOCKADE INCREASED NNOS EXPRESSION IN THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS AND IMPROVED SEXUAL BEHAVIOR DISORDER IN MALE DIABETIC RATS

You have accessJournal of UrologySexual Function/Dysfunction: Basic Research & Pathophysiology II1 Apr 2017MP81-01 CENTRAL TUMOR NECROSIS FACTOR-ALPHA BLOCKADE INCREASED NNOS EXPRESSION IN THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS AND IMPROVED SEXUAL BEHAVIOR DISORDER IN MALE DIABETIC RATS Ting Long, Huanhuan Wang, Xiaohong Ye, Wenwen Lin, Yuanyuan Zhang, and Danian Qin Ting LongTing Long More articles by this author , Huanhuan WangHuanhuan Wang More articles by this author , Xiaohong YeXiaohong Ye More articles by this author , Wenwen LinWenwen Lin More articles by this author , Yuanyuan ZhangYuanyuan Zhang More articles by this author , and Danian QinDanian Qin More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.2527AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Sexual dysfunction, including decreased libido, sexual behavior disorder and erectile dysfunction (ED), is common in male patients with diabetes mellitus (DM). We previously demonstrated that increased peripheral tumor necrosis factor alpha (TNF-a) expression, associated with inflammation in DM, contributes to ED in the rat corpus cavernosum. However, the role of TNF-a in the central pathophysiology of DM-associated male sexual dysfunction is unknown. In this study, we examined the effects of TNF-a inhibition, i.e. etanercept (ETN) via chronic intra-cerebroventricular (ICV) infusion on neuronal nitric oxide synthase (nNOS) expression in the hypothalamic paraventricular nucleus (PVN) and sexual behavior disorder in male diabetic rats. METHODS Type II male DM rats were divided into 4 groups (G), n= 12/G, and subjected to chronic ICV infusion of artificial cerebrospinal fluid (aCSF) or ETN (10 μg/kg/day) by Osmotic Pumps, with and without induction of DM: G1: non-diabetic+ICV aCSF as control; G2: non-diabetic+ICV ETN; G3: DM+ICV aCSF; and G4: DM+ICV ETN. After 4 weeks of treatments, sexual behavior, expression of TNF-a, TNFR-1, and nNOS proteins, nNOS activity, and reactive oxygen species (ROS) generation within the PVN were assessed. RESULTS Male diabetic rats with ICV aCSF treatment displayed significantly severe sexual disorder accompanied with blunted nNOS expression and activity in the PVN in addition to local upregulated TNF-a and TNFR-1 expression, and increased ROS generation compared with non-diabetic controls. The sexual behavioral parameters including mounting latency, intromission latency, the number of mountings and the number of intromissions until ejaculation, induced by the introduction of receptive females, were significantly improved in the treated group with ETN. ICV ETN significantly inhibited TNF-a and TNFR-1 expression and reduced ROS generation in the PVN in diabetic rats. In addition, ICV ETN appeared to induce marked increased in nNOS expression in the PVN of diabetic animals compared with ICV aCSF-treated diabetic rats. Activity of nNOS in the PVN was also significantly increased in ICV ETN-treated versus ICV aCSF-treated diabetic rats. CONCLUSIONS Increased TNF-a and TNFR1 expression in the hypothalamic PVN associated with DM contributes to male sexual disorder by centrally inhibiting nNOS expression and activity in the PVN via promoting local ROS generation. Central TNF-a blockade may have beneficial effects on the male sexual disorder in diabetes through improvement of NO pathway within the PVN. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e1089 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Ting Long More articles by this author Huanhuan Wang More articles by this author Xiaohong Ye More articles by this author Wenwen Lin More articles by this author Yuanyuan Zhang More articles by this author Danian Qin More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Abstract WP107: Igf-1-mediated Neuroprotection for Ischemic Stroke is Preceded by Its Actions at the Endothelial Cell Barrier

Background: Our studies show that Insulin like growth factor (IGF)-1 reduces MCAo-induced infarction in middle-aged female rats. We tested the hypothesis that IGF-1s neuroprotective effect is due to its action on the microvascular /endothelial barrier in the early acute phase of stroke. Methods: Middle-aged (12 mo) acyclic female rats were subject to intraluminal middle cerebral artery occlusion (MCAo) for 90 min followed by reperfusion and terminated 4h or 24h later. Animals received ICV infusion of artificial CSF, IGF-1 or IGF-1+JB-1. In separate experiments, we evaluated infarct volume, barrier assessment by uptake of Evan’s blue dye or histological evaluation of lectin stained microvessels. In parallel, cortical endothelial cells from middle-aged females were harvested and cultured ex vivo. Barrier properties were tested in cultures in transfer wells exposed to oxygen glucose deprivation (OGD) in the presence or absence of IGF-1 with FITC-labeled BSA in the media. Results: At 4h post MCAo, IGF-1 treatment significantly reduced brain uptake of Evan’s blue dye, while infarct volume was no different from controls. At 24h post MCAo, IGF-1 reduced infarct volume by 40% and decreased motor impairment (neurological score; p<0.05). Lectin stained microvessels in the ischemic hemisphere displayed wider lumens (normal uncompressed lumen, p<0.003) and more intense label (p<0.01) in IGF-1 treated animals as compared to either vehicle or IGF-1+JB-1 groups. Ex vivo, IGF-1 reduced the loss of cell-cell contact due to OGD and reduced the dye transfer across the monolayer. Conclusions: Our findings indicate that IGF-1 acts in the early acute phase of ischemic stroke to reduce barrier permeability, which precedes its beneficial effect on infarct volume and behavior. Further, brain endothelial cells play a crucial role in IGF-1 mediated neuroprotection in middle-aged females.

ABCA1/ApoE/HDL Pathway Mediates GW3965-Induced Neurorestoration After Stroke.

ATP-binding cassette transporter A1 (ABCA1) is a major reverse cholesterol transporter and plays critical role in the formation of brain high-density lipoprotein (HDL) cholesterol. Apolipoprotein E (ApoE) is the most abundant apolipoprotein and transports cholesterol into cells in brain. ABCA1 and ApoE are upregulated by liver-X receptors. Activation of liver-X receptors has neurorestorative benefit for stroke. The current study investigates whether ABCA1/ApoE/HDL pathway mediates GW3965, a synthetic dual liver-X receptor agonist, induced neurorestoration after stroke. Middle-aged male specific brain ABCA1-deficient (ABCA1-B/-B) and floxed-control (ABCA1fl/fl) mice were subjected to distal middle-cerebral artery occlusion (dMCAo) and gavaged with saline or GW3965 (10 mg/kg) or intracerebral infusion of artificial cerebrospinal fluid or human plasma HDL3 in ABCA1-B/-B stroke mice, starting 24 hours after dMCAo and daily until euthanization 14 days after dMCAo. No differences in the blood level of total cholesterol and triglyceride and lesion volume were found among the groups. Compared with ABCA1fl/fl ischemic mice, ABCA1-B/-B ischemic mice exhibited impairment functional outcome and decreased ABCA1/ApoE expression and decreased gray/white matter densities in the ischemic boundary zone 14 days after dMCAo. GW3965 treatment of ABCA1fl/fl ischemic mice led to increased brain ABCA1/ApoE expression, concomitantly to increased blood HDL, gray/white matter densities and oligodendrocyte progenitor cell numbers in the ischemic boundary zone, as well as improved functional outcome 14 days after dMCAo. GW3965 treatment had negligible beneficial effects in ABCA1-B/-B ischemic mice. However, intracerebral infusion of human plasma HDL3 significantly attenuated ABCA1-B/-B-induced deficits. In vitro, GW3965 treatment (5 μM) increased ABCA1/synaptophysin level and neurite/axonal outgrowth in primary cortical neurons derived from ABCA1fl/fl embryos, but not in neurons derived from ABCA1-B/-B embryos. HDL treatment (80 μg/mL) attenuated the reduction of neurite/axonal outgrowth in neurons derived from ABCA1-B/-B embryos. ABCA1/ApoE/HDL pathway, at least partially, contributes to GW3965-induced neurorestoration after stroke.

Insensitivity of well-conditioned mature sheep to central administration of a leptin receptor antagonist

Ruminants remain productive during the energy insufficiency of late pregnancy or early lactation by evoking metabolic adaptations sparing available energy and nutrients (e.g. higher metabolic efficiency and induction of insulin resistance). A deficit in central leptin signaling triggers these adaptations in rodents but whether it does in ruminants remains unclear. To address this issue, five mature ewes were implanted with intracerebroventricular (ICV) cannula in the third ventricle. They were used in two experiments with an ovine leptin antagonist (OLA) when well-conditioned (average body condition score of 3.7 on a 5 point scale). The first experiment tested the ability of OLA to antagonize leptin under in vivo conditions. Ewes received continuous ICV infusion of artificial cerebrospinal fluid (aCSF), ovine leptin (4 µg/h) or the combination of ovine leptin (4 µg/h) and its mutant version OLA (40 µg/h) for 48 h. Dry matter intake (DMI) was measured every day and blood samples were collected on the last day of infusion. ICV infusion of leptin reduced DMI by 24% (P<0.05), and this effect was completely abolished by OLA co-infusion. A second experiment tested whether a reduction in endogenous leptin signaling in the brain triggers metabolic adaptations. This involved continuous ICV infusions of aCSF or OLA alone (40 µg/h) for 4 consecutive days. The infusion of OLA did not alter voluntary DMI over the treatment period or on any individual day. OLA did not affect plasma variables indicative of insulin action (glucose, non-esterified fatty acids, insulin and the disposition of plasma glucose during an insulin tolerance test) or plasma cortisol, but tended to reduce plasma triiodothyronine and thyroxine (P<0.07). Overall, these data show that a reduction of central leptin signaling has little impact on insulin action in well-conditioned mature sheep. They also raise the possibility that reduced central leptin signaling plays a role in controlling thyroid hormone production.

Acyl Ghrelin Acts in the Brain to Control Liver Function and Peripheral Glucose Homeostasis in Male Mice

Recent evidence suggests that peripheral ghrelin regulates glucose metabolism. Here, we designed experiments to examine how central acyl ghrelin infusion affects peripheral glucose metabolism under pair-fed or ad libitum feeding conditions. Mice received intracerebroventricular (icv) infusion of artificial cerebrospinal fluid (aCSF), ghrelin, and allowed to eat ad libitum (icv ghrelin ad lib) or ghrelin and pair-fed to the aCSF group (icv ghrelin pf). Minipumps delivered acyl ghrelin at a dose of 0.25 μg/h at 0.5 μL/h for 7 days. There was no difference in daily blood glucose, insulin, glucagon, triglycerides, or nonesterified fatty acids. Body weight gain and food intake was significantly higher in icv ghrelin ad lib mice. However, both icv ghrelin ad lib and icv ghrelin pf groups exhibited heavier white adipose mass. Icv ghrelin pf mice exhibited better glucose tolerance than aCSF or icv ghrelin ad lib mice during a glucose tolerance test, although both icv ghrelin ad lib and icv ghrelin pf increased insulin release during the glucose tolerance test. Central acyl ghrelin infusion and pair feeding also increased breakdown of liver glycogen and triglyceride, and regulated genes involved in hepatic lipid and glucose metabolism. Icv ghrelin pf mice had an increase in plasma blood glucose during a pyruvate tolerance test relative to icv ghrelin ad lib or aCSF mice. Our results suggest that under conditions of negative energy (icv ghrelin pf), central acyl ghrelin engages a neural circuit that influences hepatic glucose function. Metabolic status affects the ability of central acyl ghrelin to regulate peripheral glucose homeostasis.

Angiotensin-(1–7) inhibits autophagy in the brain of spontaneously hypertensive rats

Autophagy is an important cellular process that mediates lysosomal degradation of damaged organelles, which is activated in response to a variety of stress-related diseases, including hypertension. The basal level of autophagy plays an important role in the maintenance of cellular homeostasis, whereas excessive autophagic activity leads to cell death and is considered as a contributing factor to several disorders. Recent works have demonstrated that Angiotensin-(1–7) [Ang-(1–7)] exerted its neuroprotective effects by modulating classic components of renin–angiotensin system associated with reducing oxidative stress and apoptosis in brains of spontaneously hypertensive rats (SHRs). However, the effect of Ang-(1–7) on autophagic activity in brain of hypertensive individual remains unclear. In this study, Wistar–Kyoto rats received intracerebroventricular (I.C.V.) infusion of artificial cerebrospinal fluid (aCSF) while SHRs received I.C.V. infusion of aCSF, Ang-(1–7), Mas receptor antagonist A-779, or angiotensin II type 2 receptor antagonist PD123319 for 4 weeks. Brain tissues were collected and analyzed by western blotting analysis, immunofluorescence assay, and transmission electron microscopic examination. Our study showed that infusion of Ang-(1–7) for 4 weeks inhibited the increase of microtubule-associated protein 1 light chain 3 (LC3)-II and Beclin-1 levels, as well as the autophagosome formation in SHR brain. Meanwhile, the reduction of p62 expression in SHR brain was also reversed by Ang-(1–7). Of note, the anti-autophagic effects of Ang-(1–7) were independent of blood pressure reduction and can be inhibited by A-779 and PD123319. These findings suggest that treatment with Ang-(1–7) may be useful to prevent hypertension-induced excessive autophagic activation in brain.

Angiotensin-(1-7) modulates renin–angiotensin system associated with reducing oxidative stress and attenuating neuronal apoptosis in the brain of hypertensive rats

Angiotensin-(1-7) [Ang-(1-7)] has beneficial effects against hypertension-induced damage in heart and kidney, but its effects in brain are not clear as yet. The present study aimed to investigate the protective effects of Ang-(1-7) on the physiopathologic changes caused by hypertension in brain of spontaneously hypertensive rats (SHRs). Wistar-Kyoto rats received intracerebroventricular (I.C.V.) infusion of artificial cerebrospinal fluid (aCSF) while SHRs received I.C.V. infusion of Ang-(1-7), Mas receptor antagonist A-779 and aCSF for 4 weeks. Brain tissues were collected and analyzed by western blot, enzyme immunoassay, spectrophotometric assays and terminal deoxynucleotidyl transferase-mediated dUTP end-labeling (TUNEL) staining. Our study showed that infusion of Ang-(1-7) for 4 weeks significantly reduced the expression of Angiotensin II and Angiotensin II type 1 receptors in SHR brain. Additionally, it decreased the levels of malondialdehyde and elevated total superoxide dismutase activity, which was accompanied by reductions of NADPH oxidase subunit gp91phox and inducible nitric oxide synthase in the brain of SHR. The increases of the percentage of TUNEL-positive neurons and Bax to Bcl-2 ratio in SHR brain were also attenuated by Ang-(1-7). The anti-oxidative and anti-apoptosis effects of Ang-(1-7) are independent of blood pressure reduction and can be partially abolished by A-779. These findings suggest that chronic treatment with Ang-(1-7) is beneficial to attenuate hypertension-induced physiopathologic changes in brain and may be helpful to prevent hypertension-related cerebrovascular diseases.

Acute activation of central GLP-1 receptors enhances hepatic insulin action and insulin secretion in high-fat-fed, insulin resistant mice

Glucagon-like peptide-1 (GLP-1) receptor knockout (Glp1r(-/-)) mice exhibit impaired hepatic insulin action. High fat (HF)-fed Glp1r(-/-) mice exhibit improved, rather than the expected impaired, hepatic insulin action. This is due to decreased lipogenic gene expression and triglyceride accumulation. The present studies overcome these secondary adaptations by acutely modulating GLP-1R action in HF-fed wild-type mice. The central GLP-1R was targeted given its role as a regulator of hepatic insulin action. We hypothesized that acute inhibition of the central GLP-1R impairs hepatic insulin action beyond the effects of HF feeding. We further hypothesized that activation of the central GLP-1R improves hepatic insulin action in HF-fed mice. Insulin action was assessed in conscious, unrestrained mice using the hyperinsulinemic euglycemic clamp. Mice received intracerebroventricular (icv) infusions of artificial cerebrospinal fluid, GLP-1, or the GLP-1R antagonist exendin-9 (Ex-9) during the clamp. Intracerebroventricular Ex-9 impaired the suppression of hepatic glucose production by insulin, whereas icv GLP-1 improved it. Neither treatment affected tissue glucose uptake. Intracerebroventricular GLP-1 enhanced activation of hepatic Akt and suppressed hypothalamic AMP-activated protein kinase. Central GLP-1R activation resulted in lower hepatic triglyceride levels but did not affect muscle, white adipose tissue, or plasma triglyceride levels during hyperinsulinemia. In response to oral but not intravenous glucose challenges, activation of the central GLP-1R improved glucose tolerance. This was associated with higher insulin levels. Inhibition of the central GLP-1R had no effect on oral or intravenous glucose tolerance. These results show that inhibition of the central GLP-1R deteriorates hepatic insulin action in HF-fed mice but does not affect whole body glucose homeostasis. Contrasting this, activation of the central GLP-1R improves glucose homeostasis in HF-fed mice by increasing insulin levels and enhancing hepatic insulin action.

Effects of Scutellaria baicalensis on chronic cerebral hypoperfusion-induced memory impairments and chronic lipopolysaccharide infusion-induced memory impairments

Extracts of the roots of Scutellaria baicalensis Georgi (Labiatae) have been widely used to relieve fever related to bacterial infection and inflammatory diseases in traditional Korean medicine and have been reported to be effective in brain diseases. These experiments were conducted to examine the effects of oral administration of Scutellaria baicalensis extracts on the rescue of memory impairments induced by chronic cerebral hypoperfusion or chronic lipopolysaccharide (LPS) infusion. In addition, the underlying mechanisms of these effects were investigated. In the first experiment, chronic cerebral hypoperfusion was induced in male Wister rats by bilateral common carotid artery occlusion (BCCAo). Daily administration of Scutellaria baicalensis extracts was started on 20 day after BCCAo and given for 40 days. A Morris water maze was then used to evaluate the status of the hippocampal-dependent spatial learning and hippocampal mitogen-activated protein kinase (MAPK) signaling was examined in control rats, rats with chronic cerebral hypoperfusion, and rats with chronic cerebral hypoperfusion that was administered Scutellaria baicalensis. In the second experiment, hippocampal microglial activation was induced by chronic infusions of LPS into the fourth ventricle of Fisher-344 rat brains. Daily administration of Scutellaria baicalensis extracts was started on 7 day after the surgery of LPS infusion and given for 32 days. Spatial memory and hippocampal microglial activation was then examined in control rats with an artificial cerebrospinal fluid infusion, rats with chronic LPS infusion, and rats with chronic LPS infusion that were administered Scutellaria baicalensis. Rats that received chronic cerebral hypoperfusion or chronic LPS infusion showed spatial memory impairments relative to their control rats; however, these symptoms were reduced by daily administration of Scutellaria baicalensis. Administration of Scutellaria baicalensis mitigated alterations of hippocampal MAPK signaling by chronic cerebral infusion and microglial activation by chronic LPS infusion. These results indicate that Scutellaria baicalensis may possess therapeutic potential for the prevention of Alzheimer's disease and vascular dementia.

Selective deficits in spatial working memory in the neonatal ventral hippocampal lesion rat model of schizophrenia

The neonatal ventral hippocampal lesion (NVHL) manipulation is a neurodevelopmental animal model of schizophrenia that produces abnormalities in the prefrontal cortex and nucleus accumbens, both efferent targets of the hippocampus, and leads to spatial working memory impairments. To investigate the neuroanatomical basis of spatial working memory in NVHL animals, we assessed performance in two radial arm maze tasks known to be differentially sensitive to the two hippocampal efferent pathways, and measured levels of neuronal activation (Fos immunoreactivity [Fos-IR]) in the prefrontal cortex and nucleus accumbens following task performance. Neonatal rats (postnatal day 6–8) received excitotoxic lesions of the ventral hippocampus (n = 25), or a sham procedure (infusions of artificial cerebrospinal fluid; n = 22). Upon reaching adulthood, animals were trained in either a non-delayed random foraging task or a spatial delayed win-shift task. NVHL animals were impaired on the spatial delayed win-shift task, which depends on communication between hippocampus and prefrontal cortex, but were unimpaired on the non-delayed random foraging task, which requires connections between hippocampus and nucleus accumbens. Fos-IR in the nucleus accumbens was greater in NVHL animals than in shams following the random foraging task, despite similar levels of performance, while no group differences in Fos-IR in either the nucleus accumbens or prefrontal cortex were observed following win-shift performance. These results suggest that although the NVHL manipulation disrupts development of hippocampal efferents to both the prefrontal cortex and the nucleus accumbens, the disruption of hippocampal–prefrontal pathways has the dominant behavioral effect on spatial performance in NVHL rats.

Selective Activation of Striatal Fast-Spiking Interneurons during Choice Execution

Basal ganglia circuits are essential for the organization and execution of voluntary actions. Within the striatum, fast-spiking interneurons (FSIs) are thought to tightly regulate the activity of medium-spiny projection neurons (MSNs) through feed-forward inhibition, yet few studies have investigated the functional contributions of FSIs in behaving animals. We recorded presumed MSNs and FSIs together with motor cortex and globus pallidus (GP) neurons, in rats performing a simple choice task. MSN activity was widely distributed across the task sequence, especially near reward receipt. By contrast, FSIs showed a coordinated pulse of increased activity as chosen actions were initiated, in conjunction with a sharp decrease in GP activity. Both MSNs and FSIs were direction selective, but neighboring MSNs and FSIs showed opposite selectivity. Our findings suggest that individual FSIs participate in local striatal information processing, but more global disinhibition of FSIs by GP is important for initiating chosen actions while suppressing unwanted alternatives.

Elevating intracranial pressure reverses the decrease in deoxygenated hemoglobin and abolishes the post-stimulus overshoot upon somatosensory activation in rats

BOLD fMRI localizes activated brain areas by measuring decreases of deoxygenated hemoglobin (deoxy-Hb) caused by neurovascular coupling. To date, it is unclear whether intracranial pressure (ICP) modifies deoxy-Hb signaling for brain mapping. In addition, ICP elevation can test whether the BOLD post-stimulus undershoot, a transient hypo-oxygenation following functional activation, is due to vascular compliance rather than elevated cerebral metabolic rate of oxygen (CMRO 2). We addressed these questions by studying the effect of ICP elevation on neurovascular coupling. In anesthetized rats, a cranial window was implanted over the somatosensory cortex. Using laser Doppler flowmetry and optical spectroscopy, changes in cerebral blood flow (CBF), cerebral blood volume (CBV) and deoxy-Hb were measured during electrical forepaw stimulation. Neuronal activity was monitored by somatosensory evoked potentials. ICP was elevated by subarachnoideal and intracisternal infusion of artificial cerebrospinal fluid. ICP elevation did not abrogate neurovascular coupling. However, the concomitant deoxy-Hb decrease was reduced (ICP = 14 mmHg) and reversed (ICP = 28 mmHg). Therefore, the validity of BOLD fMRI has to be questioned during increased ICP. Moreover, the amplitude of the deoxy-Hb post-stimulus overshoot was reduced with ICP elevation. CMRO 2 was not elevated during the post-stimulus response. Therefore, these data provide experimental evidence that the BOLD post-stimulus undershoot is a passive vascular phenomenon.

Hypothalamic osmoregulation is maintained across the wake-sleep cycle in the rat

In different species, rapid eye movement sleep (REMS) is characterized by a thermoregulatory impairment. It has been postulated that this impairment depends on a general insufficiency in the hypothalamic integration of autonomic function. This study aims to test this hypothesis by assessing the hypothalamic regulation of body fluid osmolality during the different wake-sleep states in the rat. Arginine-vasopressin (AVP) plasma levels were determined following intracerebroventricular (ICV) infusions of artificial cerebrospinal fluid (aCSF), either isotonic or made hypertonic by the addition of NaCl at three different concentrations (125, 250 and 500 mM). Animals were implanted with a cannula within a lateral cerebral ventricle for ICV infusions and with electrodes for the recording of the electroencephalogram. ICV infusions were made in different animals during Wake, REMS or non-REM sleep (NREMS). The results show that ICV infusion of hypertonic aCSF during REMS induced an increase in AVP plasma levels that was not different from that observed during either Wake or NREMS. These results suggest that the thermoregulatory impairment that characterizes REMS does not depend on a general impairment in the hypothalamic control of body homeostasis.