Stimulation Of Neurons Research Articles

PPARα and PPARγ are expressed in midbrain dopamine neurons and modulate dopamine- and cannabinoid-mediated behavior in mice.

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors that regulate gene expression. Δ9-tetrahydrocannabinol (Δ9-THC) is a PPARγ agonist and some endocannabinoids are natural activators of PPARα and PPARγ. However, little is known regarding their cellular distributions in the brain and functional roles in cannabinoid action. Here, we first used RNAscope in situ hybridization and immunohistochemistry assays to examine the cellular distributions of PPARα and PPARγ expression in the mouse brain. We found that PPARα and PPARγ are expressed in ~70% of midbrain dopamine (DA) neurons. In the amygdala, PPARα is expressed in ~60% ofglutamatergic neurons, while PPARγ is expressed in ~60% ofGABA neurons. However, no PPARα/γ signal was detected in GABA neurons in the nucleus accumbens. We then used a series of behavioral assays to determine the functional roles of PPARα/γ in the CNS effects of Δ9-THC. We found that optogenetic stimulation of midbrain DA neurons was rewarding as assessed by optical intracranial self-stimulation (oICSS) in DAT-cre mice. Δ9-THC and a PPARγ (but not PPARα) agonist dose-dependently inhibited oICSS. Pretreatment with PPARα or PPARγ antagonists attenuated the Δ9-THC-induced reduction in oICSS and Δ9-THC-inducedanxiogenic effects. In addition, a PPARγ agonist increased, while PPARα or PPARγ antagonists decreased open-field locomotion. Pretreatment with PPARα or PPARγ antagonists potentiated Δ9-THC-induced hypoactivity and catalepsy but failed to alter Δ9-THC-induced analgesia, hypothermia and immobility. These findings provide the first anatomical and functional evidence supporting an important role of PPARα/γ in DA-dependent behavior and cannabinoid action.

Anoctamin 4 channel currents activate glucose-inhibited neurons in the mouse ventromedial hypothalamus during hypoglycemia.

Glucose is the basic fuel essential for maintenance of viability and functionality of all cells. However, some neurons - namely, glucose-inhibited (GI) neurons - paradoxically increase their firing activity in low-glucose conditions and decrease that activity in high-glucose conditions. The ionic mechanisms mediating electric responses of GI neurons to glucose fluctuations remain unclear. Here, we showed that currents mediated by the anoctamin 4 (Ano4) channel are only detected in GI neurons in the ventromedial hypothalamic nucleus (VMH) and are functionally required for their activation in response to low glucose. Genetic disruption of the Ano4 gene in VMH neurons reduced blood glucose and impaired counterregulatory responses during hypoglycemia in mice. Activation of VMHAno4 neurons increased food intake and blood glucose, while chronic inhibition of VMHAno4 neurons ameliorated hyperglycemia in a type 1 diabetic mouse model. Finally, we showed that VMHAno4 neurons represent a unique orexigenic VMH population and transmit a positive valence, while stimulation of neurons that do not express Ano4 in the VMH (VMHnon-Ano4) suppress feeding and transmit a negative valence. Together, our results indicate that the Ano4 channel and VMHAno4 neurons are potential therapeutic targets for human diseases with abnormal feeding behavior or glucose imbalance.

Ventral tegmental area glutamate neurons establish a mu-opioid receptor gated circuit to mesolimbic dopamine neurons and regulate opioid-seeking behavior.

A two-neuron model of ventral tegmental area (VTA) opioid function classically involves VTA GABA neuron regulation of VTA dopamine neurons via a mu-opioid receptor dependent inhibitory circuit. However, this model predates the discovery of a third major type of neuron in the VTA: glutamatergic neurons. We found that about one-quarter of VTA neurons expressing the mu-opioid receptor are glutamate neurons without molecular markers of GABA co-release. Glutamate-Mu opioid receptor neurons are largely distributed in the anterior VTA. The majority of remaining VTA mu-opioid receptor neurons are GABAergic neurons that are mostlywithin the posterior VTA and do not express molecular markers of glutamate co-release. Optogenetic stimulation of VTA glutamate neurons resulted in excitatory currents recorded from VTA dopamine neurons that were reduced by presynaptic activation of the mu-opioid receptor ex vivo, establishing a local mu-opioid receptor dependent excitatory circuit from VTA glutamate neurons to VTA dopamine neurons. This VTA glutamate to VTA dopamine pathway regulated dopamine release to the nucleus accumbens through mu-opioid receptor activity in vivo. Behaviorally, VTA glutamate calcium-related neuronal activity increased following oral oxycodone consumption during self-administrationand response-contingent oxycodone-associated cues during abstinent reinstatement of drug-seeking behavior. Further, chemogenetic inhibition of VTA glutamate neurons reduced abstinent oral oxycodone-seeking behavior in male but not female mice. These results establish 1) a three-neuron model of VTA opioid function involving a mu-opioid receptor gated VTA glutamate neuron pathway to VTA dopamine neurons that controls dopamine release within the nucleus accumbens, and 2) that VTA glutamate neurons participate in opioid-seeking behavior.

Claustral neurons projecting to frontal cortex restrict opioid consumption.

The synthetic opioid fentanyl is a major contributor to the current opioid addiction crisis. We report that claustral neurons projecting to the frontal cortex limit oral fentanyl self-administration in mice. We found that fentanyl transcriptionally activates frontal-projecting claustrum neurons. These neurons also exhibit a unique suppression of Ca2+ activity upon initiation of bouts of fentanyl consumption. Optogenetic stimulation of frontal-projecting claustral neurons, intervening in this suppression, decreased bouts of fentanyl consumption. In contrast, constitutive inhibition of frontal-projecting claustral neurons in the context of a novel, group-housed self-administration procedure increased fentanyl bout consumption. This same manipulation also sensitized conditioned-place preference for fentanyl and enhanced the representation of fentanyl experience in the frontal cortex. Together, our results indicate that claustrum neurons exert inhibitory control over frontal cortical neurons to restrict oral fentanyl intake. Upregulation of activity in the claustro-frontal projection may be a promising strategy for reducing human opioid addiction.

Optogenetic Stimulation of CA1 Pyramidal Neurons at Theta Enhances Recognition Memory in Brain Injured Animals.

Abstract The hippocampus plays a prominent role in learning and memory formation. The functional integrity of this structure is often compromised after traumatic brain injury (TBI), resulting in lasting cognitive dysfunction. The activity of hippocampal neurons, particularly place cells, is coordinated by local theta oscillations. Previous studies aimed at examining hippocampal theta oscillations after experimental TBI have reported disparate findings. Using a diffuse brain injury model, the lateral fluid percussion injury (FPI; 2.0 atm), we report a significant reduction in hippocampal theta power that persists for at least three weeks after injury. We questioned whether the behavioral deficit associated with this reduction of theta power can be overcome by optogenetically stimulating CA1 neurons at theta in brain injured rats. Our results show that memory impairments in brain injured animals could be reversed by optogenetically stimulating CA1 pyramidal neurons expressing channelrhodopsin (ChR2) during learning. In contrast, injured animals receiving a control virus (lacking ChR2) did not benefit from optostimulation. These results suggest that direct stimulation of CA1 pyramidal neurons at theta may be a viable option for enhancing memory after TBI.

A STIM dependent dopamine-neuropeptide axis maintains the larval drive to feed and grow in Drosophila.

Appropriate nutritional intake is essential for organismal survival. In holometabolous insects such as Drosophila melanogaster, the quality and quantity of food ingested as larvae determines adult size and fecundity. Here we have identified a subset of dopaminergic neurons (THD') that maintain the larval motivation to feed. Dopamine release from these neurons requires the ER Ca2+ sensor STIM. Larvae with loss of STIM stop feeding and growing, whereas expression of STIM in THD' neurons rescues feeding, growth and viability of STIM null mutants to a significant extent. Moreover STIM is essential for maintaining excitability and release of dopamine from THD' neurons. Optogenetic stimulation of THD' neurons activated neuropeptidergic cells, including median neuro secretory cells that secrete insulin-like peptides. Loss of STIM in THD' cells alters the developmental profile of specific insulin-like peptides including ilp3. Loss of ilp3 partially rescues STIM null mutants and inappropriate expression of ilp3 in larvae affects development and growth. In summary we have identified a novel STIM-dependent function of dopamine neurons that modulates developmental changes in larval feeding behaviour and growth.

Intracortical Brain-machine Interface for Restoring Sensory Motor Function: Progress and Challenges

Limb loss or paralysis due to spinal cord injury has a devastating impact on quality of life. One way to restore the sensory and motor abilities lost by amputees and quadriplegics is to provide them with implants that interface directly with the central nervous system. Such Brain-machine interfaces could enable patients to exert active control over the electrical contractions of prosthetic limbs or paralysed muscles. The parallel interface can transmit sensory information about these motor outcomes back to the patient. Recent developments in algorithms for decoding motor intention from neuronal activity, using biomimetic and adaptation-based approaches and methods for delivering sensory feedback through electrical stimulation of neurons have shown promise for invasive interfaces with sensorimotor cortex, although significant challenges remain.

BQ788 reveals glial ETB receptor modulation of neuronal cholinergic and nitrergic pathways to inhibit intestinal motility: Linked to postoperative ileus.

ET-1 signalling modulates intestinal motility and inflammation, but the role of ET-1/ETB receptor signalling is poorly understood. Enteric glia modulate normal motility and inflammation. We investigated whether glial ETB signalling regulates neural-motor pathways of intestinal motility and inflammation. We studied ETB signalling using: ETB drugs (ET-1, SaTX, BQ788), activity-dependent stimulation of neurons (high K+ -depolarization, EFS), gliotoxins, Tg (Ednrb-EGFP)EP59Gsat/Mmucd mice, cell-specific mRNA in Sox10CreERT2 ;Rpl22-HAflx or ChATCre ;Rpl22-HAflx mice, Sox10CreERT2 ::GCaMP5g-tdT, Wnt1Cre2 ::GCaMP5g-tdT mice, muscle tension recordings, fluid-induced peristalsis, ET-1 expression, qPCR, western blots, 3-D LSM-immunofluorescence co-labelling studies in LMMP-CM and a postoperative ileus (POI) model of intestinal inflammation. In the muscularis externa ETB receptor is expressed exclusively in glia. ET-1 is expressed in RiboTag (ChAT)-neurons, isolated ganglia and intra-ganglionic varicose-nerve fibres co-labelled with peripherin or SP. ET-1 release provides activity-dependent glial ETB receptor modulation of Ca2+ waves in neural evoked glial responses. BQ788 reveals amplification of glial and neuronal Ca2+ responses and excitatory cholinergic contractions, sensitive to L-NAME. Gliotoxins disrupt SaTX-induced glial-Ca2+ waves and prevent BQ788 amplification of contractions. The ETB receptor is linked to inhibition of contractions and peristalsis. Inflammation causes glial ETB up-regulation, SaTX-hypersensitivity and glial amplification of ETB signalling. In vivo BQ788 (i.p., 1mg·kg-1 ) attenuates intestinal inflammation in POI. Enteric glial ET-1/ETB signalling provides dual modulation of neural-motor circuits to inhibit motility. It inhibits excitatory cholinergic and stimulates inhibitory nitrergic motor pathways. Amplification of glial ETB receptors is linked to muscularis externa inflammation and possibly pathogenic mechanisms of POI.

GABAergic Neurons in the Nucleus Accumbens are Involved in the General Anesthesia Effect of Propofol.

The mechanism underlying the hypnosis effect of propofol is still not fully understood. In essence, the nucleus accumbens (NAc) is crucial for regulating wakefulness and may be directly engaged in the principle of general anesthesia. However, the role of NAc in the process of propofol-induced anesthesia is still unknown. We used immunofluorescence, western blotting, and patch-clamp to access the activities of NAc GABAergic neurons during propofol anesthesia, and then we utilized chemogenetic and optogenetic methods to explore the role of NAc GABAergic neurons in regulating propofol-induced general anesthesia states. Moreover, we also conducted behavioral tests to analyze anesthetic induction and emergence. We found out that c-Fos expression was considerably dropped in NAc GABAergic neurons after propofol injection. Meanwhile, patch-clamp recording of brain slices showed that firing frequency induced by step currents in NAc GABAergic neurons significantly decreased after propofol perfusion. Notably, chemically selective stimulation of NAc GABAergic neurons during propofol anesthesia lowered propofol sensitivity, prolonged the induction of propofol anesthesia, and facilitated recovery; the inhibition of NAc GABAergic neurons exerted opposite effects. Furthermore, optogenetic activation of NAc GABAergic neurons promoted emergence whereas the result of optogenetic inhibition was the opposite. Our results demonstrate that NAc GABAergic neurons modulate propofol anesthesia induction and emergence.

Restoring calcium homeostasis in Purkinje cells arrests neurodegeneration and neuroinflammation in the ARSACS mouse model.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is caused by mutations in SACS gene encoding sacsin, a huge protein highly expressed in cerebellar Purkinje cells (PCs). ARSACS patients, as well as mouse models, display early degeneration of PCs, but the underlying mechanisms remain unexplored, with no available treatments.In this work, we demonstrated aberrant calcium (Ca2+) homeostasis and its impact on PC degeneration in ARSACS. Mechanistically, we found pathological elevation in Ca2+-evoked responses in Sacs-/- PCs, as the result of defective mitochondria and ER trafficking to distal dendrites and strong downregulation of key Ca2+ buffer-proteins. Alteration of cytoskeletal linkers, that we identified as specific sacsin interactors, likely account for faulty organellar trafficking in Sacs-/- cerebellum.Based on this pathogenetic cascade, we treated Sacs-/- mice with Ceftriaxone, a repurposed drug which exerts neuroprotection by limiting neuronal glutamatergic stimulation, and thus Ca2+ fluxes into PCs. Ceftriaxone treatment significantly improved motor performances of Sacs-/- mice, at both pre- and post-symptomatic stages. We correlated this effect to restored Ca2+ homeostasis, which arrests PC degeneration and attenuates secondary neuroinflammation. These findings disclose new key steps in ARSACS pathogenesis and support further optimization of Ceftriaxone in pre-clinical and clinical settings for the treatment of ARSACSpatients.

1665-P: Whole-Brain Activation Signatures of Weight-Lowering Drugs

Background: The development of effective anti-obesity therapeutics relies heavily on the ability to target CNS signaling mechanisms critically involved in the homeostatic control of body weight. To get insight into neurocircuits recruited by anti-obesity drug treatment, the present study aimed to determine whole-brain activation signatures of six different weight-lowering drug classes with documented efficacy in humans. Methods: Chow-fed mice received a single dose of lorcaserin (7 mg/kg, i.p.), rimonabant (10 mg/kg, i.p.), bromocriptine (D2 receptor agonist, 10 mg/kg, i.p.), sibutramine (10 mg/kg, p.o.), semaglutide (0.04 mg/kg, s.c.) or setmelanotide (4 mg/kg, s.c.). Brains were sampled two hours post-dosing, immunolabelled using c-Fos expression as a proxy for neuronal stimulation. Cleared whole-brains were imaged using light sheet fluorescence microscopy-deep learning pipeline enabling fully automated 3D mapping and quantitation of brain activation patterns at single-cell resolution. Results: The whole-brain analysis comprised 308 atlas-defined mouse brain areas. To enable fast and efficient data mining, an open-access web-based 3D imaging data viewer (NeuroPedia.dk) was developed. All weight-lowering drugs demonstrated brain-wide responses with notable similarities in c-Fos expression signatures. Overlapping c-Fos responses were detected in discrete homeostatic and non-homeostatic feeding centres located in the dorsal vagal complex and hypothalamus with concurrent activation of several limbic structures as well as the dopaminergic system. Conclusion: We pinpoint several overlapping brain activation signatures of various weight-lowering drugs. This shared feature suggests that weight-lowering drugs stimulate distinct homeostatic and non-homeostatic feeding centres. Future centrally acting anti-obesity compounds may be specifically designed to target key components of this neurocircuitry framework to provide more effective and sustained weight loss in obese patients. Disclosure L.S.Dalboege: Employee; Gubra aps. J.Hecksher-sørensen: Employee; Gubra ApS. M.Tozzi: None. C.G.Salinas: Employee; Gubra. T.Porsgaard: Employee; Gubra. D.D.Thorbek: Employee; Gubra APS. J.L.Skytte: Employee; Gubra ApS. U.Roostalu: Employee; Gubra. H.H.Hansen: None. J.Perens: Employee; Gubra ApS.

Optogenetic stimulation of basal forebrain cholinergic neurons prevents neuroinflammation and neuropsychiatric manifestations in pristane induced lupus mice

BackgroundNeuroinflammation has been identified as one of the primary pathogenic factors of neuropsychiatric systemic lupus erythematosus (NPSLE). However, there are no dedicated treatments available in clinics to alleviate neuroinflammation in NPSLE. It has been proposed that stimulating basal forebrain (BF) cholinergic neurons may provide potent anti-inflammatory effects in several inflammatory diseases, but its potential role in NPSLE remains unexplored. This study aims to investigate whether and how stimulating BF cholinergic neurons has a protective effect on NPSLE.ResultsOptogenetic stimulation of BF cholinergic neurons significantly ameliorated olfactory dysfunction and anxiety- and depression-like phenotype in pristane induced lupus (PIL) mice. The increased expression of adhesion molecules (P-selectin and vascular cell adhesion molecule-1 (VCAM-1)), leukocyte recruitment, blood-brain barrier (BBB) leakage were significantly decreased. Notably, the brain histopathological changes, including the elevated levels of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β), IgG deposition in the choroid plexus and lateral ventricle wall and lipofuscin accumulation in the cortical and hippocampal neurons, were also significantly attenuated. Furthermore, we confirmed the colocalization between the BF cholinergic projections and the cerebral vessels, and the expression of α7-nicotinic acetylcholine receptor (α7nAChR) on the cerebral vessels.ConclusionOur data indicate that stimulation of BF cholinergic neurons could play a neuroprotective role in the brain through its cholinergic anti-inflammatory effects on cerebral vessels. Therefore, this may be a promising preventive target for NPSLE.

Chemogenetic and optogenetic stimulation of zona incerta GABAergic neurons ameliorates motor impairment in Parkinson’s disease

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra and leads to progressive motor dysfunction. While studies have focused on the basal ganglia network, recent evidence suggests neuronal systems outside the basal ganglia are also related to PD pathogenesis. The zona incerta (ZI) is a predominantly inhibitory subthalamic region for global behavioral modulation. This study investigates the role of GABAergic neurons in the ZI in a mouse model of 6-hydroxydopamine (6-OHDA)-induced PD. First, we found a decrease in GABA-positive neurons in the ZI, and then the mice used chemogenetic/optogenetic stimulation to activate or inhibit GABAergic neurons. The motor performance of PD mice was significantly improved by chemogenetic/optogenetic activation of GABAergic neurons, and repeated chemogenetic activation of ZI GABAergic neurons increased the dopamine content in the striatum. Our work identifies the role of ZI GABAergic neurons in regulating motor behaviors in 6-OHDA-lesioned PD model mice.

Thyroxine restores hippocampal neurogenesis and synaptogenesis in a male rat model of carbimazole-induced hypothyroidism: a histological study

BackgroundAdult-onset hypothyroidism has a deleterious effect on hippocampal cognitive and memory functions. This study was performed to evaluate the possible therapeutic effect of thyroxine on hippocampus degeneration in an adult male rat model of carbimazole-induced hypothyroidism and the potentiality of spontaneous recovery. Thirty-two adult male albino rats were divided equally into four groups, as follows: I (control group), II (hypothyroidism group) received carbimazole (20 mg/kg) orally once daily for 4 weeks; III (recovery group) rats were managed as in group II, then left untreated for an additional 4 weeks to assess spontaneous recovery; and IV (thyroxine-treated group): hypothyroidism was induced as in group II, then rats received levothyroxine (20 µg/kg/day) orally for 4 weeks. Rats and their corresponding controls were sacrificed after 4 weeks in group II and after 8 weeks in groups III and IV. The levels of T3, T4, and TSH were measured. Hematoxylin and Eosin staining of thyroid and hippocampal sections was performed. Additionally, toluidine blue staining and immunohistochemical staining for PCNA, GFAP, and synaptophysin were applied to hippocampus sections. Both morphometric measurements and statistical analysis were performed.ResultsComparison of thyroxine-treated group with hypothyroidism and recovery groups revealed a significant reduction in TSH level and an increase in T3 and T4 levels, as well as improved histological architecture in both the thyroid and hippocampal sections. Hippocampal sections revealed a significant decrease in the mean area percent of GFAP, a significant increase in the mean number of PCNA-positive cells in the subgranular zone (SGZ); a niche for the adult neural stem cells (NSCs) in the hippocampus; and a significant increase in the mean area percent as well as the mean optical density of synaptophysin.ConclusionHippocampal degeneration is induced by hypothyroidism and can be restored by thyroxine replacement therapy, probably through neuronal cell preservation, synaptogenesis, and stimulation of neurogenesis in SGZ. On the other hand, spontaneous recovery from this degeneration was inadequate.

Mu Opioid Receptor–Expressing Neurons in the Dorsal Raphe Nucleus Are Involved in Reward Processing and Affective Behaviors

BackgroundMu opioid receptors (MORs) are key for reward processing, mostly studied in dopaminergic pathways. MORs are also expressed in the dorsal raphe nucleus (DRN), which is central for the modulation of reward and mood, but MOR function in the DRN remains underexplored. Here, we investigated whether MOR-expressing neurons of the DRN (DRN-MOR neurons) participate in reward and emotional responses. MethodsWe characterized DRN-MOR neurons anatomically using immunohistochemistry and functionally using fiber photometry in responses to morphine and rewarding/aversive stimuli. We tested the effect of opioid uncaging on the DRN on place conditioning. We examined the effect of DRN-MOR neuron optostimulation on positive reinforcement and mood-related behaviors. We mapped their projections and selected DRN-MOR neurons projecting to the lateral hypothalamus for a similar optogenetic experimentation. ResultsDRN-MOR neurons form a heterogeneous neuronal population essentially composed of GABAergic (gamma-aminobutyric acidergic) and glutamatergic neurons. Calcium activity of DRN-MOR neurons was inhibited by rewarding stimuli and morphine. Local photo-uncaging of oxymorphone in the DRN produced conditioned place preference. DRN-MOR neuron optostimulation triggered real-time place preference and was self-administered, promoted social preference, and reduced anxiety and passive coping. Finally, specific optostimulation of DRN-MOR neurons projecting to the lateral hypothalamus recapitulated the reinforcing effects of total DRN-MOR neuron stimulation. ConclusionsOur data show that DRN-MOR neurons respond to rewarding stimuli and that their optoactivation has reinforcing effects and promotes positive emotional responses, an activity which is partially mediated by their projections to the lateral hypothalamus. Our study also suggests a complex regulation of DRN activity by MOR opioids, involving mixed inhibition/activation mechanisms that fine-tune DRN function.

ID: 207357 Neuromodulation, Mechanism of Action, With Pathophysiological Correlation in Non-Painful Conditions: Literature Review of Current Evidence

Neuromodulation is an evolving field for both painful and non-painful conditions. Pharmacotherapy has become increasingly more advanced and targeted, yet some patients are intolerant to side effects rendering it less beneficial. Numerous studies have focused on neuromodulation techniques aimed at treating painful conditions, which show consistent data on pain reduction and beneficial long-term outcomes. Neuromodulation for pain has been proposed to work via stimulation of GABA-ergic or cholinergic neurons, which synapse on and inhibit neurons carrying painful signals. This method of activating specific neurons has been highly effective for pain; therefore, we focused on better understanding its uses for non-painful conditions such as peripheral arterial disease (PAD), urgency urinary incontinence (UUI), and Parkinson disease (PD). Thus, we performed a PubMed literature search pertaining to the use of neuromodulatory therapies for common diseases typically treated with medications.

Inflammation Modifies miR-21 Expression Within Neuronal Extracellular Vesicles to Regulate Remyelination Following Spinal Cord Injury

Cell‒cell communication following spinal cord injury (SCI) plays a key role in remyelination and neurological recovery. Although communication between neuron-neural stem cells (NSCs) affects remyelination, its precise mechanism remains unclear. The present study investigated the biological effects of extracellular vesicles (EVs) derived from neurons on the differentiation of NSCs and the remyelination of axons in a rat model for SCI. We found that that EVs derived from neurons promoted the differentiation of NSCs into oligodendrocytes and the remyelination of axons in SCI rats. However, neuron-derived EVs lost their biological effects after inflammatory stimulation of these neurons from which they originate. Further analysis demonstrated that the inflammatory stimulation on neurons upregulated miR-21 within EVs, which targeted SMAD 7 and upregulated the TGF-β/SMAD2 signaling pathway, resulting in an excess of astrocytic scar boundaries and in remyelination failure. Moreover, these effects could be abolished by miR-21 inhibitors/antagomirs. Considered together, these results indicate that inflammatory stimulation of neurons prevents remyelination following SCI via the upregulation of miR-21 expression within neuron-derived EVs, and this takes place through SMAD 7-mediated activation of the TGF-β/SMAD2 signaling pathway.Graphical Astract

Tracking the Navigation Behavior of Drosophila Larvae in Real and Virtual Odor Gradients by Using the Raspberry Pi Virtual Reality (PiVR) System.

In a closed-loop experimental paradigm, an animal experiences a modulation of its sensory input as a function of its own behavior. Tools enabling closed-loop experiments are crucial for delineating causal relationships between the activity of genetically labeled neurons and specific behavioral responses. We have recently developed an experimental platform known as "Raspberry Pi Virtual Reality" (PiVR) that is used to perform closed-loop optogenetic stimulation of neurons in unrestrained animals. PiVR is a system that operates at high temporal resolution (>30-Hz) and with low latencies. Larvae of the fruit fly Drosophila melanogaster are ideal to study the role of individual neurons in modulating behavior to aid the understanding of the neural pathways underlying various guided behaviors. Here, we introduce larval chemotaxis as an example of a navigational behavior in which an animal seeks to locate a target-in this case, the attractive source of an odor-by tracking a concentration gradient. The methodologies that we describe here combine the use of PiVR with the study of larval chemotaxis in real and virtual odor gradients, but these can also be readily adapted to other sensory modalities.

0049 Orexin 2 receptor agonist activates pre-Bötzinger complex neurons, phrenic motoneurons and the diaphragm in rodents

Abstract Introduction Neurons in the pre-Bötzinger complex are critical for the generation of inspiratory rhythm and regulation of activity of phrenic motoneurons, which control the activity of the diaphragm. Dysregulation of this neuronal network and resulting dysfunction of the diaphragm is associated with central sleep apnea (CSA). Orexins by stimulating both orexin 1 receptor (OX1R) and/or orexin 2 receptor (OX2R) can activate these neurons and the diaphragm. In this study, we assessed effects of OX2R-selective agonists on the activity of neurons in the pre-Bötzinger complex, phrenic motoneurons, and the diaphragm. Methods OX2R-selective agonists danavorexton (TAK-925) and OX-201 (a tool compound with longer plasma half-life than danavorexton in rodents) were used. OX2R and OX1R agonistic activities were examined by calcium mobilization assay in hOX2R/CHO-K1 cells and hOX1R/CHO-K1 cells, respectively. Activity of neurons in the pre-Bötzinger complex and phrenic motoneurons was investigated by electrophysiological recording in rat tissues. Activity of the diaphragm was evaluated by electromyogram recording in anesthetized rats. Respiratory activity was evaluated by whole-body plethysmography recording in mice. Results Danavorexton and OX-201 showed potent OX2R agonistic activity with 50% effective concentration (EC50) values of 5.5 nM and 8.0 nM, respectively. Danavorexton and OX-201 had >5,000-fold and 1,000-fold OX2R selectivity over OX1R, respectively. In in vitro electrophysiological analyses, danavorexton and OX-201 increased the burst frequency of neurons in the pre-Bötzinger complex (EC50: 300 nM and 760 nM, respectively) and phrenic motoneurons (EC50: 1.6 µM and not determined, respectively). Intravenous administration of OX-201 at 1 and 3 mg/kg increased burst frequency of the diaphragm in anesthetized rats and oral administration at 3 mg/kg increased respiratory activity in conscious mice. Conclusion OX2R-selective agonists may enhance respiratory function via activation of the diaphragm through stimulation of neurons in the pre-Bötzinger complex and phrenic motoneurons. OX2R agonists may have therapeutic potential in patients with CSA if enhancement of respiratory function by OX2R agonists can be observed at non-arousal concentrations. Further preclinical and clinical studies are worth conducting in patients with CSA. Support (if any) This work was conducted by Takeda Pharmaceutical Company Limited.

0048 Orexin 2 receptor agonist activates pre-Bötzinger complex neurons, hypoglossal motoneurons and the genioglossus muscle in rodents

Abstract Introduction Neurons in the pre-Bötzinger complex are critical for the generation of inspiratory rhythm and control the activity of the genioglossus muscle via activation of hypoglossal motoneurons. Activation of the genioglossus muscle causes anterior movement of the tongue and widens the upper airway. As obstructive sleep apnea (OSA) is associated with obstruction of the upper airway, activation of this neuronal pathway may be a novel therapeutic approach. Orexins have been shown to activate these neurons by stimulation of both orexin 1 receptor (OX1R) and/or orexin 2 receptor (OX2R). In this study, we assessed effects of OX2R-selective agonists on activity of neurons in the pre-Bötzinger complex, hypoglossal motoneurons, and the genioglossus muscle. Methods OX2R-selective agonists danavorexton (TAK-925) and OX-201 (a tool compound with longer plasma half-life than danavorexton in rodents) were used. Arousal effects were investigated by electroencephalogram/electromyogram recording in C57BL/6J mice and OX2R knockout mice. Activity of neurons in the pre-Bötzinger complex and hypoglossal motoneurons was investigated by electrophysiological recording in rat tissues. Activity of the genioglossus muscle was evaluated by electromyogram recording in anesthetized rats. Results Oral administration of OX-201 increased wakefulness time during sleep phase in C57BL6J mice but not in OX2R knockout mice. In in vitro electrophysiological analyses, danavorexton, and OX-201 increased the burst frequency of neurons in the pre-Bötzinger complex (EC50: 300 nM and 760 nM, respectively) and hypoglossal motoneurons (EC50: 610 nM and 260 nM, respectively). Intravenous administration of OX-201 at 1 mg/kg increased burst amplitude of the genioglossus muscle in anesthetized rats. Conclusion OX2R-selective agonists may enhance the respiratory function via activation of the genioglossus muscle through stimulation of neurons in the pre-Bötzinger complex and hypoglossal motoneurons. OX2R agonists may have therapeutic potential in patients with OSA if enhancement of respiratory function by OX2R agonists can be observed at non-arousal concentrations. Further preclinical and clinical studies are worth conducting in patients with OSA. Support (if any) This work was conducted by Takeda Pharmaceutical Company Limited.