Orexin receptor antagonists reverse aberrant dopamine neuron activity and related behaviors in a rodent model of stress-induced psychosis

Extrasynaptic localization is essential for α5GABAA receptor modulation of dopamine system function

Dopamine system dysfunction, observed in animal models with psychosis-like symptomatology, can be restored by targeting Gamma-Aminobutyric Acid type A receptors (GABAAR) containing the α5, but not α1, subunit in the ventral hippocampus (vHipp). The reason for this discrepancy in efficacy remains elusive; however, one key difference is that α1GABAARs are primarily located in the synapse, whereas α5GABAARs are mostly extrasynaptic. To test whether receptor location is responsible for this difference in efficacy, we injected a small interfering ribonucleic acid (siRNA) into the vHipp to knock down radixin, a scaffolding protein that holds α5GABAARs in the extrasynaptic space. We then administered GL-II-73, a positive allosteric modulator of α5GABAARs (α5-PAM) known to reverse shock-induced deficits in dopamine system function, to determine if shifting α5GABAARs from the extrasynaptic space to the synapse would prevent the effects of α5-PAM on dopamine system function. As expected, knockdown of radixin significantly decreased radixin-associated α5GABAARs and increased the proportion of synaptic α5GABAARs, without changing the overall expression of α5GABAARs. Importantly, GL-II-73 was no longer able to modulate dopamine neuron activity in radixin-knockdown rats, indicating that the extrasynaptic localization of α5GABAARs is critical for hippocampal modulation of the dopamine system. These results may have important implications for clinical use of GL-II-73, as periods of high hippocampal activity appear to favor synaptic α5GABAARs, thus efficacy may be diminished in conditions where aberrant hippocampal activity is present.Significance Statement Currently available treatments for psychosis, a debilitating symptom linked with several brain disorders, are inadequate. While they can help manage symptoms in some patients, they do so imperfectly. They are also associated with severe side effects that can cause discontinuation of medication. This study provides preclinical evidence that the drug, GL-II-73, possesses the ability to modulate dopamine activity, a key player in psychosis symptoms, and further provides some mechanistic details regarding these effects. Overall, this work contributes to the growing body of literature suggesting that GL-II-73 and similar compounds may possess antipsychotic efficacy.

Inactivation of hypocretin receptor-2 signaling in dopaminergic neurons induces hyperarousal and enhanced cognition but impaired inhibitory control

Hypocretin/Orexin (HCRT/OX) and dopamine (DA) are both key effectors of salience processing, reward and stress-related behaviors and motivational states, yet their respective roles and interactions are poorly delineated. We inactivated HCRT-to-DA connectivity by genetic disruption of Hypocretin receptor-1 (Hcrtr1), Hypocretin receptor-2 (Hcrtr2), or both receptors (Hcrtr1&2) in DA neurons and analyzed the consequences on vigilance states, brain oscillations and cognitive performance in freely behaving mice. Unexpectedly, loss of Hcrtr2, but not Hcrtr1 or Hcrtr1&2, induced a dramatic increase in theta (7-11 Hz) electroencephalographic (EEG) activity in both wakefulness and rapid-eye-movement sleep (REMS). DAHcrtr2-deficient mice spent more time in an active (or theta activity-enriched) substate of wakefulness, and exhibited prolonged REMS. Additionally, both wake and REMS displayed enhanced theta-gamma phase-amplitude coupling. The baseline waking EEG of DAHcrtr2-deficient mice exhibited diminished infra-theta, but increased theta power, two hallmarks of EEG hyperarousal, that were however uncoupled from locomotor activity. Upon exposure to novel, either rewarding or stress-inducing environments, DAHcrtr2-deficient mice featured more pronounced waking theta and fast-gamma (52-80 Hz) EEG activity surges compared to littermate controls, further suggesting increased alertness. Cognitive performance was evaluated in an operant conditioning paradigm, which revealed that DAHcrtr2-ablated mice manifest faster task acquisition and higher choice accuracy under increasingly demanding task contingencies. However, the mice concurrently displayed maladaptive patterns of reward-seeking, with behavioral indices of enhanced impulsivity and compulsivity. None of the EEG changes observed in DAHcrtr2-deficient mice were seen in DAHcrtr1-ablated mice, which tended to show opposite EEG phenotypes. Our findings establish a clear genetically-defined link between monosynaptic HCRT-to-DA neurotransmission and theta oscillations, with a differential and novel role of HCRTR2 in theta-gamma cross-frequency coupling, attentional processes, and executive functions, relevant to disorders including narcolepsy, attention-deficit/hyperactivity disorder, and Parkinson's disease.

Blockade of the orexin-2 receptors within the ventral tegmental area facilitates the extinction and prevents the reinstatement of methamphetamine-seeking behavior

Repeated use of methamphetamine (METH) causes severe effects on the central nervous system, associated with an increased relapse rate. The orexinergic system is highly implicated in the reward circuitry and may be a promising target for treating psychostimulant dependency. The present study aimed to investigate the involvement of the orexin system, mainly the orexin-2 receptors (OX2R) in the ventral tegmental area (VTA) in the extinction and reinstatement of METH-seeking behavior using a conditioned place preference (CPP) paradigm. To this end, animals received METH (1 mg/kg; sc) for a 5-day conditioning period. Then, in the first set of experiments, different groups of rats were given intra-VTA TCS OX2 29 (1, 3, 10, or 30 nmol/0.3 μl DMSO) as an OX2R antagonist over a 10-day extinction period. In another experiment, after the extinction period, a different set of animals received a single dose of TCS OX2 29 (1, 3, 10, or 30 nmol) before the priming dose of METH (0.25 mg/kg; sc) on the reinstatement day. The results revealed that TCS OX2 29 (10 and 30 nmol) remarkably facilitated the extinction of rewarding properties of METH (P < 0.001 for both doses). Furthermore, TCS OX2 29 (3, 10, or 30 nmol) significantly suppressed the METH-induced reinstatement (3 nmol; P < 0.05, 10 nmol; P < 0.01, and 30 nmol; P < 0.001). In conclusion, the current study revealed that the orexinergic system, specifically the VTA OX2R, is involved in METH-seeking behaviors and that manipulation of this system can be considered a potential therapeutics in treating METH dependency.

Effects of glucose modulation in lateral hypothalamus on motivated behavior to obtain sucrose in an operant task

Orexin neurons in the Lateral Hypothalamus (LH) play an important role in food seeking behavior. Approximately 60 percent of LH orexin neurons are inhibited by elevated extracellular glucose. It has been shown that elevated LH glucose decreases conditioned place preference for a food associated chamber. However, it has never been shown how modulation of LH extracellular glucose effects a rat's motivation to work for food. In this experiment we used reverse microdialysis to modulate extracellular glucose levels in LH during an operant task. Results from a progressive ratio task demonstrated that 4 mM glucose perfusion significantly decreased the animal's motivation to work for sucrose pellets while not effecting the hedonic value of the pellets. In a second experiment we demonstrated that 4 mM but not 2.5 mM glucose perfusion was sufficient to significantly decrease the number of sucrose pellets earned. Finally, we showed that modulating LH extracellular glucose mid-session from 0.7 mM to 4 mM did not affect behavior. This indicates that once feeding behavior has begun the animal becomes unresponsive to changes in extracellular glucose levels in LH. Taken together these experiments indicate that LH glucose sensing neurons play an important role in motivation to initiate feeding. However, once consumption has begun it is likely that feeding is controlled by brain regions downstream of LH.

Dual orexin/hypocretin receptor antagonism attenuates NMDA receptor hypofunction-induced attentional impairments in a rat model of schizophrenia

Schizophrenia is a neuropsychiatric condition that is associated with impaired attentional processing and performance. Failure to support increasing attentional load may result, in part, from inhibitory failure in attention-relevant cortical regions, and available antipsychotics often fail to address this issue. Orexin/hypocretin receptors are found throughout the brain and are expressed on neurons relevant to both attention and schizophrenia, highlighting them as a potential target to treat schizophrenia-associated attentional dysfunction. In the present experiment, rats (N = 14) trained in a visual sustained attention task that required discrimination of trials which presented a visual signal from trials during which no signal was presented. Once trained, rats were then co-administered the psychotomimetic N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801: 0 or 0.1 mg/kg, intraperitoneal injections) and the dual orexin receptor antagonist filorexant (MK-6096: 0, 0.1, or 1 mM, intracerebroventricular infusions) prior to task performance across six sessions. Dizocilpine impaired overall accuracy during signal trials, slowed reaction times for correctly-responded trials, and increased the number of omitted trials throughout the task. Dizocilpine-induced increases in signal trial deficits, correct response latencies, and errors of omission were reduced following infusions of the 0.1 mM, but not 1 mM, dose of filorexant. As such, orexin receptor blockade may improve attentional deficits in a state of NMDA receptor hypofunction.

GL-II-73, a Positive Allosteric Modulator of α5GABAA Receptors, Reverses Dopamine System Dysfunction Associated with Pilocarpine-Induced Temporal Lobe Epilepsy

Although seizures are a hallmark feature of temporal lobe epilepsy (TLE), psychiatric comorbidities, including psychosis, are frequently associated with TLE and contribute to decreased quality of life. Currently, there are no defined therapeutic protocols to manage psychosis in TLE patients, as antipsychotic agents may induce epileptic seizures and are associated with severe side effects and pharmacokinetic and pharmacodynamic interactions with antiepileptic drugs. Thus, novel treatment strategies are necessary. Several lines of evidence suggest that hippocampal hyperactivity is central to the pathology of both TLE and psychosis; therefore, restoring hippocampal activity back to normal levels may be a novel therapeutic approach for treating psychosis in TLE. In rodent models, increased activity in the ventral hippocampus (vHipp) results in aberrant dopamine system function, which is thought to underlie symptoms of psychosis. Indeed, we have previously demonstrated that targeting α5-containing γ-aminobutyric acid receptors (α5GABAARs), an inhibitory receptor abundant in the hippocampus, with positive allosteric modulators (PAMs), can restore dopamine system function in rodent models displaying hippocampal hyperactivity. Thus, we posited that α5-PAMs may be beneficial in a model used to study TLE. Here, we demonstrate that pilocarpine-induced TLE is associated with increased VTA dopamine neuron activity, an effect that was completely reversed by intra-vHipp administration of GL-II-73, a selective α5-PAM. Further, pilocarpine did not alter the hippocampal α5GABAAR expression or synaptic localization that may affect the efficacy of α5-PAMs. Taken together, these results suggest augmenting α5GABAAR function as a novel therapeutic modality for the treatment of psychosis in TLE.

Extrasynaptic localization is essential for α5GABA A receptor modulation of dopamine system function

Dopamine system dysfunction, observed in animal models with psychosis-like symptomatology, can be restored by targeting Gamma-Aminobutyric Acid type A receptors (GABA A R) containing the α5, but not α1, subunit in the ventral hippocampus (vHipp). The reason for this discrepancy in efficacy remains elusive; however, one key difference is that α1GABA A Rs are primarily located in the synapse, whereas α5GABA A Rs are mostly extrasynaptic. To test whether receptor location is responsible for this difference in efficacy, we injected a small interfering ribonucleic acid (siRNA) into the vHipp to knock down radixin, a scaffolding protein that holds α5GABA A Rs in the extrasynaptic space. We then administered GL-II-73, a positive allosteric modulator of α5GABA A Rs (α5-PAM) known to reverse shock-induced deficits in dopamine system function, to determine if shifting α5GABA A Rs from the extrasynaptic space to the synapse would prevent the effects of α5-PAM on dopamine system function. As expected, knockdown of radixin significantly decreased radixin-associated α5GABA A Rs and increased the proportion of synaptic α5GABA A Rs, without changing the overall expression of α5GABA A Rs. Importantly, GL-II-73 was no longer able to modulate dopamine neuron activity in radixin-knockdown rats, indicating that the extrasynaptic localization of α5GABA A Rs is critical for hippocampal modulation of the dopamine system. These results may have important implications for clinical use of GL-II-73, as periods of high hippocampal activity appear to favor synaptic α5GABA A Rs, thus efficacy may be diminished in conditions where aberrant hippocampal activity is present.

Significance Statement

Dopamine activity is known to be altered in both psychosis patients and in animal models, with promising new antipsychotics restoring normal dopamine system function. One such drug is GL-II-73, a positive allosteric modulator of α5GABA A Rs (α5-PAM). Interestingly, previous research has shown that a positive allosteric modulator of α1GABA A Rs (α1-PAM) does not share this ability, even when directly given to the ventral hippocampus, a region known to modulate dopamine activity. One potential explanation for this difference we examined in this study is that α1GABA A Rs are primarily located in the synapse, whereas α5GABA A Rs are mostly extrasynaptic. Determining the mechanism of this differential efficacy could lead to the refinement of antipsychotic treatment and improve patient outcomes overall.

Dual orexin/hypocretin receptor antagonism attenuates attentional impairments in an NMDA receptor hypofunction model of schizophrenia

Schizophrenia is a neuropsychiatric condition that is associated with impaired attentional processing and performance. Failure to support increasing attentional load may result, in part, from abnormally overactive basal forebrain projections to the prefrontal cortex, and available antipsychotics often fail to address this issue. Orexin/hypocretin receptors are expressed on corticopetal cholinergic neurons, and their blockade has been shown to decrease the activity of cortical basal forebrain outputs and prefrontal cortical cholinergic neurotransmission. In the present experiment, rats (N = 14) trained in a visual sustained attention task that required discrimination of trials which presented a visual signal from trials during which no signal was presented. Once trained, rats were then co-administered the psychotomimetic N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801: 0 or 0.1 mg/kg, intraperitoneal injections) and the dual orexin receptor antagonist filorexant (MK-6096: 0, 0.1, or 1 mM, intracerebroventricular infusions) prior to task performance across six sessions. Dizocilpine impaired overall accuracy during signal trials, slowed reaction times for correctly-responded trials, and increased the number of omitted trials throughout the task. Dizocilpine-induced increases in signal trial deficits, correct response latencies, and errors of omission were reduced following infusions of the 0.1 mM, but not 1 mM, dose of filorexant. Orexin receptor blockade, perhaps through anticholinergic mechanisms, may improve attentional deficits in a state of NMDA receptor hypofunction.

Highlights

Schizophrenia is associated with attentional deficits that may stem from abnormally reactive BF projections to the prefrontal cortexOrexin receptor antagonists decrease acetylcholine release and reduce prefrontal cortical activityThe dual orexin receptor antagonist filorexant alleviated impairments of attention following NMDA receptor blockade.

Positive Allosteric Modulation of α5-GABAA Receptors Reverses Stress-Induced Alterations in Dopamine System Function and Prepulse Inhibition of Startle

BACKGROUND

Up to 64% of patients diagnosed with posttraumatic stress disorder (PTSD) experience psychosis, likely attributable to aberrant dopamine neuron activity. We have previously demonstrated that positive allosteric modulators of α5-GABAARs can selectively decrease hippocampal activity and reverse psychosis-like physiological and behavioral alterations in a rodent model used to study schizophrenia; however, whether this approach translates to a PTSD model remains to be elucidated.

METHODS

We utilized a 2-day inescapable foot shock (IS) procedure to induce stress-related pathophysiology in male Sprague-Dawley rats. We evaluated the effects of intra-ventral hippocampus (vHipp) administration GL-II-73, an α5-GABAAR, or viral overexpression of the α5 subunit, using in vivo electrophysiology and behavioral measures in control and IS-treated rats.

RESULTS

IS significantly increased ventral tegmental area dopamine neuron population activity, or the number of dopamine neurons firing spontaneously (n = 6; P = .016), consistent with observation in multiple rodent models used to study psychosis. IS also induced deficits in sensorimotor gating, as measured by reduced prepulse inhibition of startle (n = 12; P = .039). Interestingly, intra-vHipp administration of GL-II-73 completely reversed IS-induced increases in dopamine neuron population activity (n = 6; P = .024) and deficits in prepulse inhibition (n = 8; P = .025), whereas viral overexpression of the α5 subunit in the vHipp was not effective.

CONCLUSIONS

Our results demonstrate that pharmacological intervention augmenting α5-GABAAR function, but not α5 overexpression in itself, can reverse stress-induced deficits related to PTSD in a rodent model, providing a potential site of therapeutic intervention to treat comorbid psychosis in PTSD.

Gestational buprenorphine exposure disrupts dopamine neuron activity and related behaviors in adulthood

Opioid misuse among pregnant women is rapidly increasing in the United States. The number of maternal opioid-related diagnoses increased by 131% in the last ten years, resulting in an increased number of infants exposed to opioids in utero and a subsequent increase in infants developing neonatal abstinence syndrome (NAS). The most prescribed treatment to combat maternal opioid use disorder is buprenorphine, a partial μ-opioid receptor agonist and κ-opioid receptor antagonist. Buprenorphine treatment effectively reduces NAS but has been associated with disrupted cortical development and neurodevelopmental consequences in childhood. Less is known about the long-term neurodevelopmental consequences following buprenorphine exposure in utero Previous research has shown that gestational buprenorphine exposure can induce anxiety- and depressive-like phenotypes in adult rats, suggesting that exposure to buprenorphine in utero may render individuals more susceptible to psychiatric illness in adulthood. A common pathology observed across multiple psychiatric illnesses is dopamine system dysfunction. Here, we administered the highly-abused opioid, oxycodone (10 mg/kg, i.p.) or a therapeutic used to treat opioid use disorder, buprenorphine (1 mg/kg, i.p) to pregnant Sprague Dawley rats from gestational day 11 through 21, then examined neurophysiological alterations in the mesolimbic dopamine system and dopamine-dependent behaviors in adult offspring. We found that gestational exposure to buprenorphine or oxycodone increases dopamine neuron activity in adulthood. Moreover, prenatal buprenorphine exposure disrupts the afferent regulation of dopamine neuron activity in the ventral tegmental area (VTA). Taken together, we posit that gestational buprenorphine or oxycodone exposure can have profound effects on the mesolimbic dopamine system in adulthood.Significance StatementThe opioid epidemic in the United States is a growing problem that affects people from all demographics, including pregnant women. In 2017, nearly 21,000 pregnant women reported misusing opioids during pregnancy, which can lead to many physiological and neurodevelopmental complications in infants. To combat illicit opioid use during pregnancy, buprenorphine is the priority treatment option, as it reduces illicit opioid use and alleviates symptoms of neonatal abstinence syndrome in infants. However, less is known about the long-term neurophysiological consequences of in utero opioid or buprenorphine exposure. Here, we demonstrate that both oxycodone and buprenorphine exposure, in utero, can result in aberrant dopamine system function in adult rats. These results provide evidence of potential long-lasting effects of opioid exposure during development.

A study on the effect of JNJ-10397049 on proliferation and differentiation of neural precursor cells

The orexin 2 receptor plays a central role in maintaining sleep and wakefulness. Recently, it has been shown that sleep and wakefulness orchestrate the proliferation and differentiation of oligodendrocytes. Here, we explored the role of a selective orexin 2 receptor antagonist (JNJ-10397049) in proliferation and differentiation of neural progenitor cells (NPCs). We evaluated the proliferation potential of NPCs after exposure to different concentrations of JNJ-10397049 by using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide and neurosphere assays. Moreover, the expression of differentiation markers was assessed by immunocytochemistry and real-time polymerase chain reaction. JNJ-10397049 significantly increased the proliferation of NPCs at lower concentrations. In addition, orexin 2 receptor antagonist facilitated progression of differentiation of NPCs towards oligodendroglial lineage by considerable expression of Olig2 and 2’,3’-cyclic-nucleotide 3’-phosphodiesterase as well as decreased expression of nestin marker. The results open a new avenue for future investigations in which the production of more oligodendrocytes from NPCs is needed.

Orexin deficiency affects sensorimotor gating and its amphetamine-induced impairment

The orexin neuropeptides have an important role in the regulation of the sleep/wake cycle and foraging, as well as in reward processing and emotions. Furthermore, recent research implicates the orexin system in different behavioral endophenotypes of neuropsychiatric diseases such as social avoidance and cognitive flexibility. Utilizing orexin-deficient mice, the present study tested the hypothesis that orexin is involved in two further mouse behavioral endophenotypes of neuropsychiatric disorders, i.e., sensorimotor gating and amphetamine sensitivity. The data revealed that orexin-deficient mice expressed a deficit in sensorimotor gating, measured by prepulse inhibition of the startle response. Amphetamine treatment impaired prepulse inhibition in wildtype and heterozygous orexin-deficient mice, but had no effects in homozygous orexin-deficient mice. Furthermore, locomotor activity and center time in the open field was not affected by orexin deficiency but was similarly increased or decreased, respectively, by amphetamine treatment in all genotypes. These data indicate that the orexin system modulates prepulse inhibition and is involved in mediating amphetamine's effect on prepulse inhibition. Future studies should investigate whether pharmacological manipulations of the orexin system can be used to treat neuropsychiatric diseases associated with deficits in sensorimotor gating, such as schizophrenia or attention deficit hyperactivity disorder.

Suvorexant with or without ramelteon to prevent delirium: a systematic review and meta-analysis

Delirium is a common and serious neurobehavioral syndrome, associated with prolonged hospital stays, and increased morbidity and mortality. As it remains unclear whether suvorexant with or without ramelteon prevents delirium in elderly hospitalized patients, we conducted a systematic review and meta-analysis to evaluate, searching the PubMed, Cochrane Library, Web of Science, EMBASE, and EBSCOhost databases for all randomized controlled trials (RCTs), case-control studies, and cohort studies that investigated the effects of suvorexant with or without ramelteon on delirium in adult hospitalized patients. The primary outcome was the incidence of delirium. Two randomized controlled trials, 7 cohort studies and 2 case-control studies involving 2594 patients were included in this meta-analysis. The results showed that both suvorexant alone (odds ratio (OR) = 0.30, 95% confidence interval (CI): 0.14-0.65, P = 0.002) and suvorexant with ramelteon (OR = 0.39, 95% CI 0.23-0.65, P = 0.0003) reduced the incidence of delirium in adult hospitalized patients. Six studies involved the use of benzodiazepines; subgroup analysis performed separately in the suvorexant alone and suvorexant with ramelteon groups indicated that when benzodiazepine was administered, suvorexant with ramelteon was effective at reducing the incidence of delirium (OR = 0.53, 95% CI 0.37-0.74, P = 0.0002), but no significant difference was observed for suvorexant alone (OR = 0.40, 95% CI 0.11-1.53, P = 0.18). The current literature thus supports the effectiveness of suvorexant with or without ramelteon for delirium prevention, although suvorexant alone failed to significantly reduce the incidence of delirium when benzodiazepine was administered. The present study was limited by the significant heterogeneity among the included studies, and caution should be exercised when interpreting the results. This study was registered in the PROSPERO database (CRD4202017964).

Reviewing the role of the orexinergic system and stressors in modulating mood and reward-related behaviors

In this review study, we aimed to introduce the orexinergic system as an important signaling pathway involved in a variety of cognitive functions such as memory, motivation, and reward-related behaviors. This study focused on the role of orexinergic system in modulating reward-related behavior, with or without the presence of stressors. Cross-talk between the reward system and orexinergic signaling was also investigated, especially orexinergic signaling in the ventral tegmental area (VTA), the nucleus accumbens (NAc), and the hippocampus. Furthermore, we discussed the role of the orexinergic system in modulating mood states and mental illnesses such as depression, anxiety, panic, and posttraumatic stress disorder (PTSD). Here, we narrowed down our focus on the orexinergic signaling in three brain regions: the VTA, NAc, and the hippocampus (CA1 region and dentate gyrus) for their prominent role in reward-related behaviors and memory. It was concluded that the orexinergic system is critically involved in reward-related behavior and significantly alters stress responses and stress-related psychiatric and mood disorders.

Magnetic Resonance Spectroscopy in the Ventral Tegmental Area Distinguishes Responders to Suvorexant Prior to Treatment: A 4-Week Prospective Cohort Study

Background: The ventral tegmental area (VTA; a dopaminergic nucleus) plays an important role in the sleep-wake regulation system including orexin system. In addition to neuronal activity, there is increasing evidence for an important role of glial cells (i.e., astrocytes and microglia) in these systems. The present study examined the utility of magnetic resonance spectroscopy (MRS) for detecting neural and/or glial changes in the VTA to distinguish responders from non-responders before treatment with the orexin receptor antagonist suvorexant. Methods: A total of 50 patients were screened and 9 patients were excluded. The remaining 41 patients with insomnia who have or not a psychiatric disease who were expected to receive suvorexant treatment were included in this study. We compared MRS signals in the VTA between responders to suvorexant and non-responders before suvorexant use. Based on previous reports, suvorexant responders were defined as patients who improved ≥3 points on the Pittsburgh Sleep Quality Index after 4 weeks of suvorexant use. MRS data included choline (reflects non-specific cell membrane breakdown, including of glial cells) and N-acetylaspartate (a decrease reflects neuronal degeneration). Results: Among 41 examined patients, 20 patients responded to suvorexant and 21 patients did not. By MRS, the choline/creatine and phosphorylcreatine ratio in the VTA was significantly high in non-responders compared with responders (p = 0.039) before suvorexant treatment. There was no difference in the N-acetylaspartate/creatine and phosphorylcreatine ratio (p = 0.297) between the two groups. Conclusions: Changes in glial viability in the VTA might be used to distinguish responders to suvorexant from non-responders before starting treatment. These findings may help with more appropriate selection of patients for suvorexant treatment in clinical practice. Further, we provide novel possible evidence for a relationship between glial changes in the VTA and the orexin system, which may aid in the development of new hypnotics focusing on the VTA and/or glial cells.