NMDA Receptor Glycine Binding Site Modulators for Prevention and Treatment of Ketamine Use Disorder.

Ketamine offers a fast-acting approach to relieving treatment-resistant depression, but its abuse potential is an issue of concern. As ketamine is a noncompetitive N-methyl-D-aspartate receptor (NMDAR) ion channel blocker, modulation of NMDAR might be an effective strategy to counteract the abuse liability of ketamine and even to treat ketamine use disorder. This study evaluated whether NMDAR modulators that act on glycine binding sites can decrease motivation to obtain ketamine and reduce reinstatement to ketamine-seeking behavior. Two NMDAR modulators, D-serine and sarcosine were examined. Male Sprague-Dawley rats underwent training to acquire the ability to self-administer ketamine. The motivation to self-administer ketamine or sucrose pellets was examined under a progressive ratio (PR) schedule. The reinstatement of ketamine-seeking and sucrose pellet-seeking behaviors were assessed after extinction. The results showed that both D-serine and sarcosine significantly decreased the breakpoints for ketamine and prevented reinstatement of ketamine seeking. However, these modulators did not alter motivated behavior for sucrose pellets, the ability of the cue and sucrose pellets to reinstate sucrose-seeking behavior or spontaneous locomotor activity. These findings indicate that two NMDAR modulators can specifically reduce the measures of motivation and relapse for ketamine in rats, suggesting that targeting the glycine binding site of the NMDAR is a promising approach for preventing and treating ketamine use disorder.

Revisiting the cerebral hemodynamics of awake, freely moving rats with repeated ketamine self-administration using a miniature photoacoustic imaging system.

Significance: Revealing the dynamic associations between brain functions and behaviors is a significant challenge in neurotechnology, especially for awake subjects. Imaging cerebral hemodynamics in awake animal models is important because the collected data more realistically reflect human disease states. Aim: We previously reported a miniature head-mounted scanning photoacoustic imaging (hmPAI) system. In the present study, we utilized this system to investigate the effects of ketamine on the cerebral hemodynamics of normal rats and rats subjected to prolonged ketamine self-administration. Approach: The cortical superior sagittal sinus (SSS) was continuously monitored. The full-width at half-maximum (FWHM) of the photoacoustic (PA) A-line signal was used as an indicator of the SSS diameter, and the number of pixels in PA B-scan images was used to investigate changes in the cerebral blood volume (CBV). Results: We observed a significantly higher FWHM (blood vessel diameter) and CBV in normal rats injected with ketamine than in normal rats injected with saline. For rats subjected to prolonged ketamine self-administration, no significant changes in either the blood vessel diameter or CBV were observed. Conclusions: The lack of significant change in prolonged ketamine-exposed rats was potentially due to an increased ketamine tolerance. Our device can reliably detect changes in the dilation of cortical blood vessels and the CBV. This study validates the utility of the developed hmPAI system in an awake, freely moving rat model for behavioral, cognitive, and preclinical cerebral disease studies.

Beneficial effects of atypical antipsychotics on object recognition deficits after adolescent toluene exposure in mice: involvement of 5-HT1A receptors.

Background: Inhalant (e.g. toluene) misuse by adolescents has been linked to psychosis and persistent cognitive deficits. Identifying effective strategies to improve cognitive deficits following chronic toluene misuse is critical. 5-HT1A receptor has been proposed as a target for the treatment of cognitive deficits.Objectives: We compared the effects of antipsychotics on recognition deficits after adolescent toluene exposure in mice and elucidated the role of 5-HT1A receptors in the cognition-improving effects of antipsychotics.Methods: Male NMRI mice (n = 279) received one injection per day of either toluene (750 mg/kg) or corn oil at postnatal days 35-39 and 42-46. Thereafter, the acute and subchronic effects of haloperidol, aripiprazole, or clozapine on toluene-induced recognition deficits were evaluated by novel object recognition test.Results: Acute administration of aripiprazole (p < .05) and clozapine (p < .01), but not haloperidol, significantly attenuated the toluene-induced recognition deficits. Pretreatment with 5-HT1A receptor antagonist WAY -100,635 (p < .05) blocked their beneficial effects. Moreover, 5-HT1A receptor agonist buspirone (p < .01) ameliorated the toluene-induced recognition deficits, which was reversed by WAY -100,635 (p < .001). Finally, after repeated treatment with clozapine, aripiprazole, and buspirone daily for 14 days, the impaired object recognition in toluene-exposed mice was significantly improved (p < .05) and the beneficial effects lasted for at least 2 weeks (p < .05).Conclusions: The results indicate that clozapine and aripiprazole, which display 5-HT1A agonist properties, restored cognitive deficits in mice induced by adolescent toluene exposure. These findings suggest that these antipsychotics should be further explored as a potential treatment option for cognitive deficits in patients with psychosis associated with toluene exposure.

Effects of Vibration Resistance Exercises on EMG and Skeletal Muscle Hemodynamics.

Objectives: Past studies show that vibration can stimulate muscle activity and improve muscle performance. However, further verification is needed on the effects of different vibration frequencies combined with different muscle strength exercise intensities on EMG activity and skeletal muscle hemodynamics. Methods: We recruited 27 male college athletes for 40%, 60%, and 80% maximum voluntary contraction (MVC) tests at the vibration frequencies of 0 Hz, 10 Hz, 20 Hz, and 30 Hz. We collected EMG activity signals using wireless EMGs and skeletal muscle hemodynamic parameters using a near-infrared spectrometer. Results: At an 80% MVC intensity of the rectus femoris, the mean, peak, and area of EMG at 30 Hz were significantly increased, compared with those at 0 Hz. At a 40% MVC intensity with vibration frequencies of 10 Hz, 20 Hz, and 30 Hz, the HHb of skeletal muscles was significantly increased, while the O2Hb and TSI were significantly decreased, compared with those at 0 Hz. Conclusions: We conclude that high frequency and strongly vibrated muscle strength exercise can improve EMG activity, while vibration and low-intensity muscle strength exercise could increase the oxygen consumption of skeletal muscles.

Does Far-Infrared Therapy Improve Peritoneal Function and Reduce Recurrent Peritonitis in Peritoneal Dialysis Patients?

The use of peritoneal dialysis in end-stage renal disease is increasing in clinical practice. The main purpose of this study was to evaluate the effect of far-infrared radiation therapy on inflammation and the cellular immunity of patients undergoing peritoneal dialysis. We recruited 56 patients undergoing peritoneal dialysis, and we included 32 patients for the experimental group and 24 patients from the control group in the final analysis. The experimental evaluation in our study was as follows: (1) We used abdominal computed tomography to explore the changes in abdominal blood vessels. (2) We compared the effects of peritoneal dialysis using blood glucose, HbAlC, albumin, urea nitrogen, creatinine, white blood cells, hs-CRP; peritoneal Kt/V of peritoneal function, and eGFR. (3) We compared the cytokines' concentrations in the two groups while controlling for the other cytokines. Results and Discussion: (1) There was no significant difference in the abdominal blood vessels of the experimental group relative to the control group according to abdominal CT over the 6 months. (2) Our study demonstrates statistically significant effects of FIR therapy on the following parameters: creatinine (p = 0.039 *) and hs-CRP (p < 0.001 **) levels decreased significantly, and eGFR (p = 0.043 *), glucose (p < 0.001 **), and albumin (p = 0.048 *) levels increased significantly. Our study found that in the experimental group, creatinine and hs-CRP levels decreased significantly due to FIR therapy for 6 months. However, our study also found that the glucose level was significantly different after FIR therapy for 6 months. Peritoneal dialysis combined with FIR can reduce the side effects of the glucose in the dialysis buffer, which interferes with peritoneal inflammation and peritoneal mesothelial cell fibrosis. (3) In addition, we also found that no statistically significant difference in any inflammatory cytokine after FIR therapy. IFN-γ (p = 0.124), IL-12p70 (p = 0.093), IL-18 (p = 0.213), and TNF-α (p = 0.254) did not exhibit significant improvements after peritoneal dialysis with FIR treatment over 6 months. Conclusions: We found that the effectiveness of peritoneal dialysis was improved significantly with FIR therapy, and significant improvements in the peritoneal permeability and inflammatory response were observed.

Betaine prevents and reverses the behavioral deficits and synaptic dysfunction induced by repeated ketamine exposure in mice.

As an N-methyl-D-aspartate (NMDA) receptor inhibitor, ketamine has become a popular recreational substance and currently is used to address treatment-resistant depression. Since heavy ketamine use is associated with persisting psychosis, cognitive impairments, and neuronal damage, the safety of ketamine treatment for depression should be concerned. The nutrient supplement betaine has been shown to counteract the acute ketamine-induced psychotomimetic effects and cognitive dysfunction through modulating NMDA receptors. This study aimed to determine whether the adjunctive or subsequent betaine treatment would improve the enduring behavioral disturbances and hippocampal synaptic abnormality induced by repeated ketamine exposure. Mice received ketamine twice daily for 14 days, either combined with betaine co-treatment or subsequent betaine post-treatment for 7 days. Thereafter, three-chamber social approach test, reciprocal social interaction, novel location/object recognition test, forced swimming test, and head-twitch response induced by serotonergic hallucinogen were monitored. Data showed that the enduring behavioral abnormalities after repeated ketamine exposure, including disrupted social behaviors, recognition memory impairments, and increased depression-like and hallucinogen-induced head-twitch responses, were remarkably improved by betaine co-treatment or post-treatment. Consistently, betaine protected and reversed the reduced hippocampal synaptic activity, such as decreases in field excitatory post-synaptic potentiation (fEPSP), long-term potentiation (LTP), and PSD-95 levels, after repeated ketamine treatment. These results demonstrated that both co-treatment and post-treatment with betaine could effectively prevent and reverse the adverse behavioral manifestations and hippocampal synaptic plasticity after repeated ketamine use, suggesting that betaine can be used as a novel adjunct therapy with ketamine for treatment-resistant depression and provide benefits for ketamine use disorders.

N, N-dimethylglycine Protects Behavioral Disturbances and Synaptic Deficits Induced by Repeated Ketamine Exposure in Mice.

Ketamine, an N-methyl-d-aspartate receptor (NMDAR) blocker, is gaining ground as a treatment option for depression. The occurrence of persistent psychosis and cognitive impairment after repeated use of ketamine remains a concern. N, N-dimethylglycine (DMG) is a nutrient supplement and acts as an NMDAR glycine site partial agonist. The objective of this study was to assess whether DMG could potentially prevent the behavioral and synaptic deficits in mice after repeated ketamine exposure. Male ICR mice received ketamine (20 mg/kg) from postnatal day (PN) 33-46, twice daily, for 14 days. The locomotor activity, novel location recognition test (NLRT), novel object recognition test (NORT), social interaction test, head twitch response induced by serotonergic hallucinogen, and the basal synaptic transmission and long-term potentiation (LTP) in the hippocampal slices were monitored after repeated ketamine treatment. Furthermore, the protective effects of repeated combined administration of DMG (30 and 100 mg/kg) with ketamine on behavioral abnormalities and synaptic dysfunction were assessed. The results showed that mice exhibited memory impairments, social withdrawal, increased head twitch response, reduced excitatory synaptic transmission, and lower LTP after repeated ketamine exposure. The ketamine-induced behavioral and synaptic deficits were prevented by co-treatment with DMG. In conclusion, these findings may pave a new path forward to developing a combination formula with ketamine and DMG for the treatment of depression and other mood disorders.

Cervical Total Disc Replacement and Heterotopic Ossification: A Review of Literature Outcomes and Biomechanics.

Anterior cervical discectomy and fusion (ACDF) immobilizes surgical segments and can lead to the development of adjacent segment degeneration and adjacent segment disease. Thus, cervical total disc replacement (CTDR) has been developed with the aim to preserve the biomechanics of spine. However, heterotopic ossification (HO), a complication following CTDR, can reduce the segmental range of motion (ROM) and defects the motion-preservation benefit of CTDR. The pathological process of HO in CTDR remains unknown. HO has been suggested to be a self-defense mechanism in response to the non-physiological biomechanics of the cervical spine following CTDR. The current literature review is concerned with the association between the biomechanical factors and HO formation and the clinical significance of HO in CTDR. Endplate coverage, disc height, segmental angle, and center of rotation may be associated with the development of HO. The longer the follow-up, the higher the rate of ROM-limiting HO. Regardless of the loss of motion-preservation benefit of CTDR in patients with HO, CTDR confers patients with a motion-preservation period before the development of ROM-limiting HO. This may delay the development of adjacent segment degeneration compared with ACDF. Future clinical studies should explore the association between HO and changes in biomechanical factors of the cervical spine.

The Changes in Cervical Biomechanics After CTDR and Its Association With Heterotopic Ossification: A Systematic Review and Meta-analysis.

STUDY DESIGN: A systematic review and meta-analysis. OBJECTIVES: Cervical total disc replacement (CTDR) can preserve range of motion (ROM) of the operated spinal segment in cadaver studies. Evidence is less clear in clinical trials. The present study aims to investigate the differences in cervical biomechanics before and after CTDR and its association with heterotopic ossification (HO) development. METHOD: Articles that reported the rate of HO and ≥1 difference in cervical biomechanics were included in quantitative analyses. We pooled the mean difference (MD) of cervical biomechanics before and after CTDR. Subgroup analyses and metaregression analyses were conducted to identify potential contributors to heterogeneity. RESULTS: Of the 599 studies screened, 35 studies were included in the final analysis. In comparison with preoperative values, ROM of the spinal segment inferior (MD: 0.38; 95% CI: 0.02 to 0.74) and superior (MD: 0.43; 95% CI: 0.12 to 0.75) to the surgical spinal segment, functional spinal unit (FSU) angle (MD: 2.23; 95% CI: 1.11 to 3.35), and C2/C7 Cobb angle (MD: 3.49; 95% CI: 1.73 to 5.25) significantly increased after CTDR. In contrast, FSU and cervical ROM at baseline were no different from follow-up. On multivariable meta-regression analyses, HO and ROM-limiting HO were not associated with changes in cervical biomechanics. Single-level CTDR and duration of follow-up were associated with changes in cervical biomechanics. CONCLUSION: Our study reported the pooled mean of biomechanics at baseline and final follow-up and their differences. The changes in biomechanics were not associated with the rates of HO and ROM-limiting HO.

Increased behavioral and neuronal responses to a hallucinogenic drug after adolescent toluene exposure in mice: Effects of antipsychotic treatment.

Toluene has been characterized as a non-classical hallucinogen drug through activation of 5-HT2A receptors and antagonism of NMDA receptors. It remains unclear whether psychotic symptoms after long-term and intense toluene exposure are associated with abnormalities in 5-HT2A receptor function. The present study examined whether the responses to a hallucinogenic 5-HT2A receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) were altered in a mouse model of toluene psychosis. Male NMRI mice were subchronically treated with toluene during adolescence. Reciprocal social interaction test and novel object recognition test were conducted to confirm the persistent behavioral deficits in adulthood. Subsequently, DOI-induced head twitch, c-Fos and Egr-2 expression, field potentials in the medial prefrontal cortex (mPFC), and the levels of 5-HT2A, 5-HT1A and mGlu2 receptors in the mPFC were monitored. Toluene exposure during adolescence produced social and memory impairments and enhanced DOI-induced behavioral, molecular and electrophysiological responses, but did not change the levels of 5-HT2A, 5-HT1A or mGlu2 receptors in the mPFC. Moreover, the effects of haloperidol and risperidone on the behavioral deficits and hyper-responsiveness to DOI after adolescent toluene exposure were compared. When administered after adolescent toluene exposure, risperidone could reverse social withdrawal, cognitive impairment and hypersensitivity to DOI, whereas haloperidol was only beneficial for social withdrawal. These findings suggest that increased functionality of 5-HT2A receptors may play a critical role in solvent-induced psychosis and recommend the antipsychotics with more selective 5-HT2A receptor antagonism as the first-line treatment for solvent-induced psychosis.

Prevalence of and Risk Factors for Heterotopic Ossification After Cervical Total Disc Replacement: A Systematic Review and Meta-Analysis.

STUDY DESIGN: A systematic review and meta-analysis. OBJECTIVES: The results from previous meta-analyses are limited by the small number of included studies. Moreover, the risk factors of heterotopic ossification (HO) have not been well studied. Therefore, this study aims to estimate the prevalence of HO after cervical total disc replacement (CTDR) at different follow-up time points and explore potential risk factors for HO. METHODS: We searched databases to identify eligible studies that reported the rate of HO after CTDR. The pooled prevalence of HO, according to different grades of HO, length of follow-up and types of prosthesis, and 95% confidence intervals (CIs) were calculated. Multivariable meta-regression analyses were performed to identify factors that may contribute to the heterogeneity between estimates. RESULTS: Of the 94 studies included, 82 studies reported an overall rate of HO, encompassing a total of 5861 cervical spinal levels that underwent CTDR. The overall pooled prevalence of HO was 32.5% (95% CI 26.7% to 38.4%). Single-level CTDR was associated with a higher overall rate of HO. When the rate of HO was stratified by McAfee/Mehren classification, the pooled prevalence of range of motion (ROM)-limiting HO was 11.0% (95% CI 9.2% to 12.8%). Latest publication, single-level CTDR, longer follow-up period, and studies published outside were associated with a higher rate of ROM-limiting HO. CONCLUSIONS: We provide a comprehensive overview of the prevalence of different grades of HO. This meta-analysis also identifies and rules out some risk factors for HO after CTDR.

Muscle activation and intermuscular coherence during forward and backward pedaling.

The purpose of this study was to investigate muscle activity and intermuscular coherence of the rectus femoris (RF) and biceps femoris (BF) during forward (FW) and backward (BW) pedaling. Sixteen healthy volunteers performed FW and BW pedaling in 30, 45, and 60 revolutions per minute (RPM), while electromyographic (EMG) signals of the RF and BF were recorded bilaterally to determine integral EMG and intermuscular coherence. BW pedaling showed a statistically significant larger EMG activity on the left BF (P = 0.023) in 30 RPM; on the left BF (P = 0.01), right BF (P = 0.05), and right RF (P = 0.006) in 45 RPM, and on the left BF (P = 0.014) and right RF (P = 0.011) in 60 RPM than FW pedaling. In 45 RPM, higher coherence was demonstrated on the left leg (P = 0.011) during the left flexor and right extensor phases and on the right leg (P = 0.043) during the right flexor and left extensor phases in BW compared with FW pedaling. In 60 RPM, higher coherence was observed on both legs (left, P = 0.037; right, P < 0.001) during the left flexor and right extensor phases in BW compared with FW pedaling. Our results suggest that BW pedaling increased the muscle activity of both biarticular muscles and intermuscular coherence.

Comparison of M6-C and Mobi-C cervical total disc replacement for cervical degenerative disc disease in adults.

BACKGROUND: Cervical total disc replacement (CTDR) is complicated by adjacent segment degeneration (ASD). Since non-physiological spine kinematics after CTDR was postulated to cause ASD, M6-C prosthesis has been developed to better replicate the natural kinematics of the intervertebral disc. This retrospective cohort study aims to compare the short-term outcomes between patients receiving either the M6-C or Mobi-C prostheses. METHODS: Patients who had refractory radiculopathy and/or myelopathy secondary to cervical degenerative disc disease and underwent CTDR between March 2004 and April 2017 were included. All CTDRs were performed by a single surgeon at a single institution. Self-reported clinical outcomes and radiological parameters were evaluated at baseline and final follow-up between March 2004 and April 2018. RESULTS: Sixty-two patients with greater than 1-year follow-up or who developed HO within 12 months of surgery, were included in the study. The mean radiological follow-up was 29.0 months (3-84 months), which includes 7 patients with less than 12 months follow-up who also developed HO. The changes in clinical and radiological measures were comparable between M6-C and Mobi-C prostheses. Thirty-seven out of 52 spinal segments (71.2%) and 10 out of 16 spinal segments (62.5%) developed HO in M6-C and Mobi-C group respectively. There was no significant difference in the rate of HO between the two groups. CONCLUSIONS: No short-term differences were found in clinical or radiological outcomes between patients who received either the M6-C or Mobi-C prosthesis. Further randomized trials with a long-term follow-up period are warranted to determine the safety and efficacy of M6-C prosthesis.

Lamotrigine attenuates the motivation to self-administer ketamine and prevents cue- and prime-induced reinstatement of ketamine-seeking behavior in rats.

BACKGROUND: Lamotrigine is an anticonvulsant drug used in the treatment of epilepsy and bipolar disorder. A case report has demonstrated that a ketamine addict experienced a significant reduction in craving and ketamine use after taking lamotrigine. The present study determined whether lamotrigine can reduce the motivation for ketamine and prevent the relapse to ketamine seeking behavior in rats. METHODS: Male Sprague-Dawley rats were trained to respond for intravenous ketamine (0.5 mg/kg/infusion) self-administration or food pellets. The effects of lamotrigine on the motivation for ketamine or food were assessed using breakpoint test under a progressive ratio (PR) paradigm. Furthermore, the effects of lamotrigine on reinstatement of ketamine-seeking and food-seeking behaviors were examined after extinction. RESULTS: Lamotrigine significantly decreased the breakpoint for ketamine and prevented cue- and ketamine priming-induced reinstatement of ketamine seeking behavior. However, lamotrigine did not affect the breakpoint for food reinforcement, cue-induced reinstatement of food-seeking behavior, or spontaneous locomotor activity. CONCLUSIONS: Our data reveal that lamotrigine is capable of attenuating the reinforcing efficacy of ketamine and reducing ketamine craving and relapse risk, which lays the foundation for conducting clinical trials in patients with ketamine use disorder.

Effects of sarcosine and N, N-dimethylglycine on NMDA receptor-mediated excitatory field potentials.

BACKGROUND: Sarcosine, a glycine transporter type 1 inhibitor and an N-methyl-D-aspartate (NMDA) receptor co-agonist at the glycine binding site, potentiates NMDA receptor function. Structurally similar to sarcosine, N,N-dimethylglycine (DMG) is also N-methyl glycine-derivative amino acid and commonly used as a dietary supplement. The present study compared the effects of sarcosine and DMG on NMDA receptor-mediated excitatory field potentials (EFPs) in mouse medial prefrontal cortex brain slices using a multi-electrode array system. RESULTS: Glycine, sarcosine and DMG alone did not alter the NMDA receptor-mediated EFPs, but in combination with glutamate, glycine and its N-methyl derivatives significantly increased the frequency and amplitude of EFPs. The enhancing effects of glycine analogs in combination with glutamate on EFPs were remarkably reduced by the glycine binding site antagonist 7-chlorokynurenate (7-CK). However, DMG, but not sarcosine, reduced the frequency and amplitude of EFPs elicited by co-application of glutamate plus glycine. D-cycloserine, a partial agonist at the glycine binding site on NMDA receptors, affected EFPs in a similar manner to DMG. Furthermore, DMG, but not sarcosine, reduced the frequencies and amplitudes of EFPs elicited by glutamate plus D-serine, another endogenous ligand for glycine binding site. CONCLUSIONS: These findings suggest that sarcosine acts as a full agonist, yet DMG is a partial agonist at glycine binding site of NMDA receptors. The molecular docking analysis indicated that the interactions of glycine, sarcosine, and DMG to NMDA receptors are highly similar, supporting that the glycine binding site of NMDA receptors is a critical target site for sarcosine and DMG.

Betaine enhances antidepressant-like, but blocks psychotomimetic effects of ketamine in mice.

Ketamine is emerging as a new hope against depression, but ketamine-associated psychotomimetic effects limit its clinical use. An adjunct therapy along with ketamine to alleviate its adverse effects and even potentiate the antidepressant effects might be an alternative strategy. Betaine, a methyl derivative of glycine and a dietary supplement, has been shown to have antidepressant-like effects and to act like a partial agonist at the glycine site of N-methyl-D-aspartate receptors (NMDARs). Accordingly, betaine might have potential to be an adjunct to ketamine treatment for depression. The antidepressant-like effects of ketamine and betaine were evaluated by forced swimming test and novelty suppressed feeding test in mice. Both betaine and ketamine produced antidepressant-like effects. Furthermore, we determined the effects of betaine on ketamine-induced antidepressant-like and psychotomimetic behaviors, motor incoordination, hyperlocomotor activity, and anesthesia. The antidepressant-like responses to betaine combined with ketamine were stronger than their individual effects. In contrast, ketamine-induced impairments in prepulse inhibition, novel object recognition test, social interaction, and rotarod test were remarkably attenuated, whereas ketamine-induced hyperlocomotion and loss of righting reflex were not affected by betaine. These findings revealed that betaine could enhance the antidepressant-like effects, yet block the psychotomimetic effects of ketamine, suggesting that betaine can be considered as an add-on therapy to ketamine for treatment-resistant depression and suitable for the treatment of depressive symptoms in patients with schizophrenia.

N,N-dimethylglycine differentially modulates psychotomimetic and antidepressant-like effects of ketamine in mice.

Ketamine, a dissociative anesthetic, produces rapid and sustained antidepressant effects at subanesthtic doses. However, it still inevitably induces psychotomimetic side effects. N,N-dimethylglycine (DMG) is a derivative of the amino acid glycine and is used as a dietary supplement. Recently, DMG has been found acting at glycine binding site of the N-methyl-d-aspartate receptor (NMDAR). As blockade of NMDARs is one of the main mechanisms responsible for the action of ketamine on central nervous system, DMG might modulate the behavioral responses to ketamine. The present study determined the effects of DMG on the ketamine-induced psychotomimetic, anesthetic and antidepressant-like effects in mice. DMG pretreatment reversed the ketamine-induced locomotor hyperactivity and impairment in the rotarod performance, novel location and novel object recognition tests, and prepulse inhibition. In addition, DMG alone exhibited antidepressant-like effects in the forced swim test and produced additive effects when combined with ketamine. However, DMG did not affect ketamine-induced anesthesia. These results reveal that DMG could antagonize ketamine's psychotomimetic effects, yet produce additive antidepressant-like effects with ketamine, suggesting that DMG might have antipsychotic potential and be suitable as an add-on therapy to ketamine for patients with treatment-resistant depression.

Integrating Image-Based High-Content Screening with Mouse Models Identifies 5-Hydroxydecanoate as a Neuroprotective Drug for Paclitaxel-Induced Neuropathy.

Chemotherapy-induced neurotoxicity is a common adverse effect of cancer treatment. No medication has been shown to be effective in the prevention or treatment of chemotherapy-induced neurotoxicity. This study aimed to discover potential neuroprotective drugs for paclitaxel-induced neurotoxicity. An image-based high-content platform was first developed to screen for potential neuroprotective drugs. The screening system comprised of automated image acquisition and multiparameter analysis, including neuronal viability, neurite outgrowth, and synaptogenesis. By this platform, we obtained a candidate list from compound libraries. In the drug screening from compound libraries of ion channel ligands, REDOX and GABAergic ligands, 5-hydroxydecanoate (5-HD) exhibited the most significant neuroprotective effects against paclitaxel-induced neurotoxicity in both cortical and dorsal root ganglion (DRG) neurons. In mouse behavioral tests, 5-HD restored the thermal sensitivity and alleviated mechanical allodynia induced by paclitaxel. Electron micrographs of sciatic nerve revealed that 5-HD reduced the damages caused by paclitaxel in the nonmyelinated and smaller myelinated fibers. The mechanistic study on DRG neurons suggested that 5-HD rescued the dysregulation of intracellular calcium homeostasis provoked by paclitaxel. Importantly, 5-HD did not jeopardize the antitumor effect of paclitaxel in tumor xenograft models. In conclusion, we established an imaged-based high-content screening platform and a protocol for verifying the neuroprotective effect in vivo, by which 5-HD was identified and validated as a potential neuroprotective drug for paclitaxel-induced neuropathy.

The group II metabotropic glutamate receptor agonist LY379268 reduces toluene-induced enhancement of brain-stimulation reward and behavioral disturbances.

RATIONALE: Toluene, a widely abused solvent with demonstrated addictive potential in humans, hasbeen reported to negatively modulate N-methyl-D-aspartate receptors (NMDARs) and alter glutamatergicneurotransmission. The group II metabotropic glutamate receptor (mGluR) agonist LY379268 has beenshown to regulate glutamate release transmission and NMDAR function and block toluene-induced locomotorhyperactivity. However, remaining unknown is whether group II mGluRs are involved in the toluene-induced reward-facilitating effect and other behavioral manifestations. OBJECTIVES: The present study evaluated the effects of LY379268 on toluene-induced reward enhancement, motor incoordination, recognition memory impairment, and social interaction deficits. RESULTS: Our data demonstrated that LY379268 significantly reversed the toluene-induced lowering of intracranial self-stimulation (ICSS) thresholds and impairments in novel object recognition, rotarod performance, and social interaction with different potencies. CONCLUSIONS: These results indicate a negative modulatory role of group II mGluRs in acute toluene-induced reward-facilitating and behavioral effects and suggest that group II mGluR agonists may have therapeutic potential for toluene addiction and the prevention of toluene intoxication caused by occupational or intentional exposure.