OBJECTIVE: Research and clinical application of transcranial magnetic stimulation (TMS) for adolescents with major depressive disorder (MDD) has advanced slowly. Significant gaps persist in our understanding of optimized, age-specific protocols and dosing strategies. This study aimed to compare the clinical effects of 1 Hz versus 10 Hz TMS regimens and examine a biomarker-informed treatment approach with glutamatergic intracortical facilitation (ICF).
METHODS: Participants with moderate-to-severe symptoms of MDD were randomized to 30 sessions of left prefrontal 1 Hz or 10 Hz TMS, stratified by baseline ICF measures. The primary clinical outcome measure was the Children\'s Depression Rating Scale, Revised (CDRS-R). The CDRS-R and ICF biomarker were collected weekly.
RESULTS: Forty-one participants received either 1 Hz (n = 22) or 10 Hz (n = 19) TMS treatments. CDRS-R scores improved compared to baseline in both 1 Hz and 10 Hz groups. For participants with low ICF at baseline, the overall least squares means of CDRS-R scores over the 6-week trial showed that depressive symptom severity was lower for the group treated with 1 Hz TMS than for those who received 10 Hz TMS. There were no significant changes in weekly ICF measurements across the 6 weeks of TMS treatment.
CONCLUSIONS: Low ICF may reflect optimal glutamatergic N-methyl-d-aspartate (NMDA) receptor activity that facilitates the therapeutic effect of 1 Hz TMS through long-term depression-like mechanisms on synaptic plasticity. The stability of ICF suggests that it is a tonic, trait-like measure of NMDA receptor-mediated neurotransmission, with potential utility to inform parameter selection for therapeutic TMS in adolescents with MDD.

Stinels are a novel class of N-methyl-d-aspartate glutamate receptor (NMDAR) positive allosteric modulators. We explored mechanism of action and NR2 subtype specificity of the stinel zelquistinel (ZEL) in HEK 293 cells expressing recombinant NMDARs. ZEL potently enhanced NMDAR current at NR2A (EC50 = 9.9 ± 0.5 nM) and NR2C-containing (EC50 = 9.7 ± 0.6 nM) NMDARs, with a larger ceiling enhancement at NR2B-NMDAR (EC50 = 35.0 ± 0.7 nM), while not affecting NR2D-containing NMDARs. In cells expressing NR2A and NR2C-containing NMDARs, ZEL exhibited an inverted-U dose-response relation, with a low concentration enhancement and high concentration suppression of NMDAR currents. Extracellular application of ZEL potentiated NMDAR receptor activity via prolongation of NMDAR currents. Replacing the slow Ca2+ intracellular chelator EGTA with the fast chelator BAPTA blocked ZEL potentiation of NMDARs, suggesting an action on intracellular Ca2+-calmodulin-dependent inactivation (CDI). Consistent with this mechanism of action, removal of the NR1 intracellular C-terminus, or intracellular infusion of a calmodulin blocking peptide, blocked ZEL potentiation of NMDAR current. In contrast, BAPTA did not prevent high-dose suppression of current, indicating this effect has a different mechanism of action. These data indicate ZEL is a novel positive allosteric modulator that binds extracellularly and acts through a unique long-distance mechanism to reduce NMDAR CDI, eliciting enhancement of NMDAR current. The critical role that NMDARs play in long-term, activity-dependent synaptic plasticity, learning, memory and cognition, suggests dysregulation of CDI may contribute to psychiatric disorders such as depression, schizophrenia and others, and that the stinel class of drugs can restore NMDAR-dependent synaptic plasticity by reducing activity-dependent CDI.

Temporomandibular joint osteoarthritis (TMJOA) is a severe form of temporomandibular joint disorders (TMD), and orofacial inflammatory allodynia is one of its common symptoms which lacks effective treatment. N-methyl-D-aspartate receptor (NMDAR), particularly its subtypes GluN2A and GluN2B, along with gap junctions (GJs), are key players in the mediation of inflammatory pain. However, the precise regulatory mechanisms of GluN2A, GluN2B, and GJs in orofacial inflammatory allodynia during TMJ inflammation still remain unclear. Here, we established the TMJ inflammation model by injecting Complete Freund\'s adjuvant (CFA) into the TMJ and used Cre/loxp site-specific recombination system to conditionally knock out (CKO) GluN2A and GluN2B in the trigeminal ganglion (TG). Von-frey test results indicated that CFA-induced mechanical allodynia in the TMJ region was relieved in GluN2A and GluN2B deficient mice. In vivo, CFA significantly up-regulated the expression of GluN2A and GluN2B, Gjb1, Gjb2, Gjc2 and Panx3 in the TG, and GluN2A and GluN2B CKO played different roles in mediating the expression of Gjb1, Gjb2, Gjc2 and Panx3. In vitro, NMDA up-regulated the expression of Gjb1, Gjb2, Gjc2 and Panx3 in satellite glial cells (SGCs) as well as promoted the intercellular communication between SGCs, and GluN2A and GluN2B knocking down (KD) altered the expression and function differently. NMDAR regulated Gjb1 and Panx3 through ERK1/2 pathway, and mediated Gjb2 and Gjc2 through MAPK, PKA, and PKC intracellular signaling pathways. These findings shed light on the distinct functions of GluN2A and GluN2B in mediating peripheral sensitization induced by TMJ inflammation in the TG, offering potential therapeutic targets for managing orofacial inflammatory allodynia.

BACKGROUND: The high comorbidity between schizophrenia and cigarette smoking points to a possible shared heritable factor predisposing individuals with schizophrenia to nicotine addiction. The N-methyl-D-aspartate (NMDA) receptor has been highly implicated in both schizophrenia and nicotine addiction.
METHODS: In the present study, we used mice with a null mutation on the serine racemase gene (srr), an established risk gene for schizophrenia, which encodes the enzyme to produce the NMDA receptor co-agonist D-serine, to model the pathology of schizophrenia and to determine whether NMDA receptor hypofunction reduced the ability of srr-/- mice to identify nicotine\'s subjective effects. Established nicotine discrimination procedures were used to train srr-/- and wild-type (WT) mice to discriminate 0.4 mg/kg nicotine under a 10-response fixed-ratio (FR10) schedule of food reinforcement.
RESULTS: Results show that WT mice reliably acquired 0.4 mg/kg nicotine discrimination in about 54 training session, whereas srr-/- mice failed to acquire robust 0.4 mg/kg nicotine discrimination even after extended (>70) training sessions. These results show that NDMA receptor hypofunction in srr-/- mice decreased sensitivity to the interoceptive effects of nicotine.
CONCLUSIONS: Projected to humans, NMDA receptor hypofunction caused by mutations to the serine racemase gene in schizophrenia may reduce sensitivity to nicotine\'s subjective effects leading to increased nicotine consumption to produce the same effects as those unaffected by schizophrenia.
CONCLUSIONS: There is high comorbidity between schizophrenia and nicotine dependence as well as possible shared genetic risk factors between the two. The serine racemase knockout mouse (srr-/-) with NMDA receptor hypofunction has been developed a model for schizophrenia. We found that srr-/- mice were unable to acquire 0.4 mg/kg nicotine discrimination, whilst wild-type mice readily discriminated nicotine. These results show that decreased NMDA receptor function present in srr-/- mice and patients with schizophrenia may result in reduced sensitivity to nicotine\'s interoceptive effects, leading to increased nicotine consumption to produce the same subjective effects as those unaffected by schizophrenia.

Monosodium glutamate (MSG) administration has been shown to pronounce hypertension and oxidative status with increased renal blood flow (RBF), however, the precise mechanisms of action have never been demonstrated. This study aimed to investigate the MSG action by studying the alteration in renal architecture and specific protein expression in 2-kidney-1-clip hypertensive comparing to sham operative normotensive rats. The administered doses of MSG were 80, 160, or 320 mg/kg BW daily for 8 weeks. Using routine chemical staining, the congestion of glomerular capillaries, a lesser renal corpuscles and glomeruli size, a widen Bowman capsule\'s space, an increase in mesangial cell proliferation and mesangial matrix, renal interstitial fibrosis, focal cloudy swelling of renal tubular epithelial cells were observed. Immunological study revealed an increase in the expression of N-methyl-D-aspartate receptor (NMDA-R) and endothelial nitric oxide synthase (eNOS) but a decrease in neuronal NOS (nNOS). It is suggested that MSG may upregulate the NMDA-R levels which responsible for the oxidative stress, glomerular injury, and renal interstitial fibrosis. The NMDA-R may also stimulate eNOS overexpression which resulted in renal microvascular dilatation, a raise in RBF and GFR, and natriuresis and diuresis promotion. Long-term exposure of MSG may trigger adaptation of tubuloglomerular feedback through nNOS downregulation.

OBJECTIVE: To explore the rapid antidepressant potential and the underlying mechanism of Chaihu Shugan San (CSS) in female mice.
METHODS: Liquid chromatography mass spectrometry (LC-MS)/MS was used to determine the content of main components in CSS to determine its stability. Female C57BL/6J mice were randomly divided into 4 groups, including control (saline), vehicle (saline), CSS (4 g/kg) and ketamine (30 mg/kg) groups. Mice were subjected to irregular stress stimulation for 4 weeks to establish the chronic mild stress (CMS) model, then received a single administration of drugs. Two hours later, the behavioral tests were performed, including open field test, tail suspension test (TST), forced swimming test (FST), novelty suppression feeding test (NSF), and sucrose preference test (SPT). Western blot analysis was used to detect the expression levels of N-methyl-D-aspartate receptor (NMDA) subtypes [N-methyl-D-aspartate receptor 1 (NR1), NR2A, NR2B], synaptic proteins [synapsin1 and post synaptic density protein 95 (PSD95)], and brain-derived neurotrophic factor (BDNF). Moreover, the rapid antidepressant effect of CSS was tested by pharmacological technologies and optogenetic interventions that activated glutamate receptors, NMDA.
RESULTS: Compared with the vehicle group, a single administration of CSS (4 g/kg) reversed all behavioral defects in TST, FST, SPT and NSF caused by CMS (P<0.05 or P<0.01). CSS also significantly decreased the expressions of NMDA subtypes (NR1, NR2A, NR2B) at 2 h in hippocampus of mice (all P<0.01). In addition, similar to ketamine, CSS increased levels of synaptic proteins and BDNF (P<0.05 or P<0.01). Furthermore, the rapid antidepressant effects of CSS were blocked by transient activation of NMDA receptors in the hippocampus (all P<0.01).
CONCLUSIONS: Rapid antidepressant effects of CSS by improving behavioral deficits in female CMS mice depended on rapid suppression of NMDA receptors and activation of synaptic proteins.

OBJECTIVE: Postoperative pain remains one of the most common complaints after surgery, and appropriate treatments are limited.
METHODS: We therefore investigated the effect of the anti-nociceptive properties of magnesium sulfate (MgSO4), an N-methyl-D-aspartate (NMDA) receptor antagonist, on incision-induced postoperative pain and peripheral and central nervous system inflammation.
RESULTS: We found that local MgSO4 administration dose-dependently increases paw withdrawal latency, indicating reduced peripheral postoperative pain. Furthermore, MgSO4 inhibited the expression of interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) and phosphorylation of the NMDA receptor NR1 subunit in injured paw tissue and significantly attenuated microglial and astrocytic activation in the ipsilateral lumbar spinal cord dorsal horn.
CONCLUSIONS: Locally administered MgSO4 has potential for development as an adjunctive therapy for preventing central nociceptive sensitization.

Colon cancer is on the rise in both men and women. In addition to traditional treatment methods, herbal treatments from complementary and alternative medicine are actively followed. Naturally derived from plants, thymoquinone (TQ) has drawn a lot of attention in the field of cancer treatment. MK-801, an N-methyl-D-aspartate agonist, is used to improve memory and plasticity, but it has also lately been explored as a potential cancer treatment. This study aimed to determine the roles of N-Methyl-D-Aspartate agonists and Thymoquinone on mitochondria and apoptosis. HT-29 cells were treated with different TQ and MK-801 concentrations. We analyzed cell viability, apoptosis, and alteration of mitochondria. Cell viability significantly decreased depending on doses of TQ and MK-801. Apoptosis and mitochondrial dysfunctions induced by low and high doses of TQ and MK-801. Our study emphasizes the need for further safety evaluation of MK-801 due to the potential toxicity risk of TQ and MK-801. Optimal and toxic doses of TQ and MK-801 were determined for the treatment of colon cancer. It should be considered as a possibility that colon cancer can be treated with TQ and MK-801.

N-methyl-d-aspartate receptors (NMDARs) are the main class of ionotropic receptors for the excitatory neurotransmitter glutamate. They play a crucial role in the permeability of Ca2+ ions and excitatory neurotransmission in the brain. Being heteromeric receptors, they are composed of several subunits, including two obligatory GluN1 subunits (eight splice variants) and regulatory GluN2 (GluN2A~D) or GluN3 (GluN3A~B) subunits. Widely distributed in the brain, they regulate other neurotransmission systems and are therefore involved in essential functions such as synaptic transmission, learning and memory, plasticity, and excitotoxicity. The present review will detail the structure, composition, and localization of NMDARs, their role and regulation at the glutamatergic synapse, and their impact on cognitive processes and in neurodegenerative diseases (Alzheimer\'s, Huntington\'s, and Parkinson\'s disease). The pharmacology of different NMDAR antagonists and their therapeutic potentialities will be presented. In particular, a focus will be given on fluoroethylnormemantine (FENM), an investigational drug with very promising development as a neuroprotective agent in Alzheimer\'s disease, in complement to its reported efficacy as a tomography radiotracer for NMDARs and an anxiolytic drug in post-traumatic stress disorder.

OBJECTIVE: To investigate the effects of hydrogen therapy on epileptic seizures in rats with refractory status epilepticus and the underlying mechanisms.
METHODS: Status epilepticus was induced using pilocarpine. The effects of hydrogen treatment on epilepsy severity in model rats were then monitored using Racine scores and electroencephalography (EEG), followed by western blot of plasma membrane N-methyl-D-aspartate receptor subtype 2B (NR2B) and phosphorylated NR2B expression. We also generated a cellular epilepsy model using Mg2+-free medium and used polymerase chain reaction to investigate the neuroprotective effects of hydrogen.
RESULTS: There were no significant differences in Racine scores between the hydrogen and control groups. EEG amplitudes were lower in the hydrogen treatment group than in the control group. In epilepsy model rats, hippocampal cell membrane NR2B expression and phosphorylation increased gradually over time. Although hippocampal cell membrane NR2B expression was not significantly different between the two groups, NR2B phosphorylation levels were significantly lower in the hydrogen group. Hydrogen treatment also increased superoxide dismutase, mitochondrial (SOD2) expression.
CONCLUSIONS: Hydrogen treatment reduced EEG amplitudes and NR2B phosphorylation; it also decreased neuronal death by reducing oxidative stress. Hydrogen may thus be a potential treatment for refractory status epilepticus by inhibiting membrane NR2B phosphorylation and oxidative stress.