almorexant and Disease-Models--Animal

To explore the effects of different doses of almorexant (an dual orexin receptor antagonist) on learning and memory in Alzheimer's disease (AD) mice.. Forty-four APP/PS1 (model of Alzheimer's disease; AD) mice were randomly divided into 4 groups: the control group (CON) and those that received 10 mg/kg almorexant (low dose; LOW), 30 mg/kg almorexant (medium dose; MED) and 60 mg/kg almorexant (high dose; HIGH). During the 28-day intervention period, mice received an intraperitoneal injection at the beginning of the light period (6:00 am). The effects of different doses of almorexant on learning and memory and 24-hour sleep-wake behaviour were assessed by immunohistochemical staining. The above continuous variables are expressed as the mean ± standard deviation (SD), and then univariate regression analysis and generalized estimating equations were performed to compare the groups; these results are expressed as the mean difference (MD) and 95% confidence interval (CI). The statistical software used STATA 17.0 MP.. Forty-one mice completed the experiment (3 died: 2 mice in the HIGH group and 1 mouse in the CON group). Compared with the CON group, the LOW group (MD=6803 s, 95% CI: 4470 to 9137 s), MED group (MD=14,473 s, 95% CI: 12,140-16,806 s) and the HIGH group (MD=24,505 s, 95% CI: 22,052-26,959 s) had significantly longer sleep durations. The Y maze results showed that LOW group (MD=0.14,95%CI: 0.078-0.20) and MED group (MD=0.14,95%CI = 0.074-0.20) mice compared to the CON group, and the low-medium dose of Almorexant did not damage the short-term learning and memory performance of APP / PS1 (AD) mice.Compared with the CON, LOW, and MED groups, the HIGH group exhibited a significant decrease in the Aβ plaque-positive area in the cortex (MD= -0.030, 95% CI: -0.035 to -0.025; MD=-0.049, 95% CI: -0.054 to -0.044; and MD=-0.07, 95% CI: -0.076 to -0.066, respectively).. The moderate dose of almorexant (30 mg/kg) prolonged the sleep duration of APP/PS1 (AD) mice to a greater extent than the low dose (10 mg/kg) without altering learning and memory. The MED mice showed a good sleep response and a small residual effect on the next day. High-dose (60 mg / kg) almorexant impaired behavioral learning and memory performance in mice.Compared to the CON group and the LOW group, the MED group exhibited improved working memory. Thus, treatment with almorexant may reduce β-amyloid deposition in AD, slowing neurodegeneration. Additional studies are needed to determine the mechanism of action.

Topics: Acetamides; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Disease Models, Animal; Hippocampus; Maze Learning; Mice; Mice, Transgenic

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

BPH/2J mice are a genetic model of hypertension associated with an overactive sympathetic nervous system. Orexin is a neuropeptide which influences sympathetic activity and blood pressure. Orexin precursor mRNA expression is greater in hypothalamic tissue of BPH/2J compared with normotensive BPN/3J mice. To determine whether enhanced orexinergic signaling contributes to the hypertension, BPH/2J and BPN/3J mice were preimplanted with radiotelemetry probes to compare blood pressure 1 hour before and 5 hours after administration of almorexant, an orexin receptor antagonist. Mid frequency mean arterial pressure power and the depressor response to ganglion blockade were also used as indicators of sympathetic nervous system activity. Administration of almorexant at 100 (IP) and 300 mg/kg (oral) in BPH/2J mice during the dark-active period (2 hours after lights off) markedly reduced blood pressure (-16.1 ± 1.6 and -11.0 ± 1.1 mm Hg, respectively;P<0.001 compared with vehicle). However, when almorexant (100 mg/kg, IP) was administered during the light-inactive period (5 hours before lights off) no reduction from baseline was observed (P=0.64). The same dose of almorexant in BPN/3J mice had no effect on blood pressure during the dark (P=0.79) or light periods (P=0.24). Almorexant attenuated the depressor response to ganglion blockade (P=0.018) and reduced the mid frequency mean arterial pressure power in BPH/2J mice (P<0.001), but not BPN/3J mice (P=0.70). Immunohistochemical labeling revealed that BPH/2J mice have 29% more orexin neurons than BPN/3J mice which are preferentially located in the lateral hypothalamus. The results suggest that enhanced orexinergic signaling contributes to sympathetic overactivity and hypertension during the dark period in BPH/2J mice.

Topics: Acetamides; Administration, Oral; Animals; Biomarkers; Blood Pressure Determination; Disease Models, Animal; Dose-Response Relationship, Drug; Hypertension; Injections, Intraperitoneal; Isoquinolines; Male; Mice; Mice, Transgenic; Motor Activity; Orexins; Pressoreceptors; Random Allocation; Reference Values; Renin-Angiotensin System; Sympathetic Nervous System; Treatment Outcome

Humans with narcolepsy and orexin/ataxin-3 transgenic (TG) mice exhibit extensive, but incomplete, degeneration of hypo-cretin (Hcrt) neurons. Partial Hcrt cell loss also occurs in Parkinson disease and other neurologic conditions. Whether Hcrt antagonists such as almorexant (ALM) can exert an effect on the Hcrt that remains after Hcrt neurodegeneration has not yet been determined. The current study was designed to evaluate the hypnotic and cataplexy-inducing efficacy of a Hcrt antagonist in an animal model with low Hcrt tone and compare the ALM efficacy profile in the disease model to that produced in wild-type (WT) control animals.. Counterbalanced crossover study.. Home cage.. Nine TG mice and 10 WT mice.. ALM (30, 100, 300 mg/kg), vehicle and positive control injections, dark/active phase onset.. During the 12-h dark period after dosing, ALM exacerbated cataplexy in TG mice and increased nonrapid eye movement sleep with heightened sleep/wake fragmentation in both genotypes. ALM showed greater hypnotic potency in WT mice than in TG mice. The 100 mg/kg dose conferred maximal promotion of cataplexy in TG mice and maximal promotion of REM sleep in WT mice. In TG mice, ALM (30 mg/ kg) paradoxically induced a transient increase in active wakefulness. Core body temperature (Tb) decreased after acute Hcrt receptor blockade, but the reduction in Tb that normally accompanies the wake-to-sleep transition was blunted in TG mice.. These complex dose- and genotype-dependent interactions underscore the importance of effector mechanisms downstream from Hcrt receptors that regulate arousal state. Cataplexy promotion by ALM warrants cautious use of Hcrt antagonists in patient populations with Hcrt neurodegeneration, but may also facilitate the discovery of anticataplectic medications.. Black SW; Morairty SR; Fisher SP; Chen TM; Warrier DR; Kilduff TS. Almorexant promotes sleep and exacerbates cataplexy in a murine model of narcolepsy. SLEEP 2013;36(3):325-336.

Topics: Acetamides; Analysis of Variance; Animals; Cataplexy; Cross-Over Studies; Disease Models, Animal; Electroencephalography; Electromyography; Intracellular Signaling Peptides and Proteins; Isoquinolines; Male; Mice; Mice, Inbred C57BL; Narcolepsy; Neurons; Neuropeptides; Orexins; Sleep; Wakefulness

The rat fear-potentiated startle (FPS) paradigm is a translational model of conditioned fear involving central amygdala pathways of the brain. Hypothalamic orexin neurons have input-output projections to the amygdala; they modulate vigilance and stress-related responses.. To investigate whether the transient pharmacological blockade of orexin receptors moderates the conditioned fear response.. F344 rats received acute oral treatment with the dual orexin receptor antagonist almorexant (30-300 mg/kg) or with one of the clinically effective anxiolytics diazepam (1-10 mg/kg), buspirone (10-100 mg/kg), fluoxetine (3-30 mg/kg), and sertraline (10-100 mg/kg). Drug effects on startle responses were assessed in both fear- and non-fear-conditioned rats; on forepaw grip and horizontal wire motor performance, and on elevated plus maze (EPM) behavior.. Diazepam and almorexant both dose-dependently decreased FPS in the presence of the fear-conditioned stimulus (CS; light) more prominently than background startle in absence of the CS (dark). Diazepam induced myorelaxation and reduced startle responses in control non-fear-conditioned rats. Almorexant had no myorelaxant effects and left startle responses under light in non-fear-conditioned rats intact. On the EPM, diazepam showed anxiolytic-like effects, almorexant not. Buspirone demonstrated anxiolytic-like effects on FPS by simultaneously reducing CS-related startle and increasing no-CS-background startle. Fluoxetine did not affect FPS, whereas sertraline showed anxiogenic-like effects.. Almorexant reduced FPS, but did not affect EPM behavior. Almorexant's overall pattern of effects on FPS was comparable to but less pronounced than that of the anxiolytic benzodiazepine diazepam. The endogenous orexin system actively contributes to fear-conditioned startle reactions in the rat.

Topics: Acetamides; Animals; Anti-Anxiety Agents; Anxiety; Behavior, Animal; Disease Models, Animal; Dose-Response Relationship, Drug; Fear; Intracellular Signaling Peptides and Proteins; Isoquinolines; Male; Maze Learning; Neuropeptides; Orexin Receptors; Orexins; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Receptors, Neuropeptide; Reflex, Startle

Growing evidence indicates that an increase of orexin (or hypocretin) signaling is involved in the pathophysiology of major depression, but little is known regarding the causal link between the orexinergic system and depressive-like states. Here we blocked orexin receptors in mice subjected to unpredictable chronic mild stress (UCMS) to investigate putative antidepressant-like effects of this treatment, as well as the underlying mechanisms. BALB/c mice were exposed to 9 weeks of UCMS and from the third week onward treated daily with fluoxetine (20 mg/kg per day, per os) or with the dual orexin receptor antagonist almorexant (100 mg/kg per day, per os). The effects of UCMS regimen and pharmacological treatments were assessed by physical measures and behavioral testing. The dexamethasone suppression test was performed to examine the integrity of the negative feedback of the hypothalamic-pituitary-adrenal (HPA) axis, and immunohistochemical markers were used to assess cell proliferation (Ki-67), immature newborn neurons (doublecortin), and mature newborn neurons (5-bromo-2'-deoxyuridine/NeuN) in the dorsal and ventral parts of the hippocampus. Our results show that 7 weeks of fluoxetine or almorexant treatments counteract the UCMS-induced physical and behavioral alterations. Both treatments prevented the HPA axis dysregulation caused by UCMS, but only fluoxetine reversed the UCMS-induced decrease of hippocampal cell proliferation and neurogenesis, while chronic almorexant treatment decreased cell proliferation and neurogenesis specifically in the ventral hippocampus. Taken together, this is the first evidence that pharmacological blockade of the orexinergic system induces a robust antidepressant-like effect and the restoration of stress-related HPA axis defect independently from a neurogenic action.

Topics: Acetamides; Animals; Antidepressive Agents; Behavior, Animal; Biomarkers; Bromodeoxyuridine; Cell Proliferation; Depression; Disease Models, Animal; Doublecortin Domain Proteins; Fluoxetine; Hypothalamo-Hypophyseal System; Intracellular Signaling Peptides and Proteins; Isoquinolines; Ki-67 Antigen; Mice; Mice, Inbred BALB C; Microtubule-Associated Proteins; Neurogenesis; Neuropeptides; Orexin Receptors; Orexins; Pituitary-Adrenal System; Receptors, G-Protein-Coupled; Receptors, Neuropeptide

Amyloid-beta (Abeta) accumulation in the brain extracellular space is a hallmark of Alzheimer's disease. The factors regulating this process are only partly understood. Abeta aggregation is a concentration-dependent process that is likely responsive to changes in brain interstitial fluid (ISF) levels of Abeta. Using in vivo microdialysis in mice, we found that the amount of ISF Abeta correlated with wakefulness. The amount of ISF Abeta also significantly increased during acute sleep deprivation and during orexin infusion, but decreased with infusion of a dual orexin receptor antagonist. Chronic sleep restriction significantly increased, and a dual orexin receptor antagonist decreased, Abeta plaque formation in amyloid precursor protein transgenic mice. Thus, the sleep-wake cycle and orexin may play a role in the pathogenesis of Alzheimer's disease.

Topics: Acetamides; Alzheimer Disease; Amyloid beta-Peptides; Animals; Antigens, Surface; Circadian Rhythm; Disease Models, Animal; Extracellular Fluid; Female; Hippocampus; Humans; Intracellular Signaling Peptides and Proteins; Isoquinolines; Light; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neuropeptides; Orexin Receptors; Orexins; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Neuropeptide; Signal Transduction; Sleep; Sleep Deprivation; Wakefulness