Predicting the effects of per- and polyfluoroalkyl substance mixtures on peroxisome proliferator-activated receptor alpha activity in vitro.

Human exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous, with mixtures of PFAS detected in drinking water, food, household dust, and other exposure sources. Animal toxicity studies and human epidemiology indicate that PFAS may act through shared mechanisms including activation of peroxisome proliferator activated receptor α (PPARα). However, the effect of PFAS mixtures on human relevant molecular initiating events remains an important data gap in the PFAS literature. Here, we tested the ability of modeling approaches to predict the effect of diverse PPARα ligands on receptor activity using Cos7 cells transiently transfected with a full length human PPARα (hPPARα) expression construct and a peroxisome proliferator response element-driven luciferase reporter. Cells were treated for 24 h with two full hPPARα agonists (pemafibrate and GW7647), a full and a partial hPPARα agonist (pemafibrate and mono(2-ethylhexyl) phthalate), or a full hPPARα agonist and a competitive antagonist (pemafibrate and GW6471). Receptor activity was modeled with three additive approaches: effect summation, relative potency factors (RPF), and generalized concentration addition (GCA). While RPF and GCA accurately predicted activity for mixtures of full hPPARα agonists, only GCA predicted activity for full and partial hPPARα agonists and a full agonist and antagonist. We then generated concentration response curves for seven PFAS, which were well-fit with three-parameter Hill functions. The four perfluorinated carboxylic acids (PFCA) tended to act as full hPPARα agonists while the three perfluorinated sulfonic acids (PFSA) tended to act as partial agonists that varied in efficacy between 28-67 % of the full agonist, positive control level. GCA and RPF performed equally well at predicting the effects of mixtures with three PFCAs, but only GCA predicted experimental activity with mixtures of PFSAs and a mixture of PFCAs and PFSAs at ratios found in the general population. We conclude that of the three approaches, GCA most accurately models the effect of PFAS mixtures on hPPARα activity in vitro. Understanding the differences in efficacy with which PFAS activate hPPARα is essential for accurately predicting the effects of PFAS mixtures. As PFAS can activate multiple nuclear receptors, future analyses should examine mixtures effects in intact cells where multiple molecular initiating events contribute to proximate effects and functional changes.

Quantal Ca2+ release mediated by very few IP3 receptors that rapidly inactivate allows graded responses to IP3.

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca2+ channels that link extracellular stimuli to Ca2+ signals. Ca2+ release from intracellular stores is "quantal": low IP3 concentrations rapidly release a fraction of the stores. Ca2+ release then slows or terminates without compromising responses to further IP3 additions. The mechanisms are unresolved. Here, we synthesize a high-affinity partial agonist of IP3Rs and use it to demonstrate that quantal responses do not require heterogenous Ca2+ stores. IP3Rs respond incrementally to IP3 and close after the initial response to low IP3 concentrations. Comparing functional responses with IP3 binding shows that only a tiny fraction of a cell's IP3Rs mediate incremental Ca2+ release; inactivation does not therefore affect most IP3Rs. We conclude, and test by simulations, that Ca2+ signals evoked by IP3 pulses arise from rapid activation and then inactivation of very few IP3Rs. This allows IP3Rs to behave as increment detectors mediating graded Ca2+ release.

An engineered IL-2 partial agonist promotes CD8+ T cell stemness.

Adoptive transfer of antigen-specific T cells represents a major advance in cancer immunotherapy, with robust clinical outcomes in some patients1. Both the number of transferred T cells and their differentiation state are critical determinants of effective responses2,3. T cells can be expanded with T cell receptor (TCR)-mediated stimulation and interleukin-2, but this can lead to differentiation into effector T cells4,5 and lower therapeutic efficacy6, whereas maintenance of a more stem-cell-like state before adoptive transfer is beneficial7. Here we show that H9T, an engineered interleukin-2 partial agonist, promotes the expansion of CD8+ T cells without driving terminal differentiation. H9T led to altered STAT5 signalling and mediated distinctive downstream transcriptional, epigenetic and metabolic programs. In addition, H9T treatment sustained the expression of T cell transcription factor 1 (TCF-1) and promoted mitochondrial fitness, thereby facilitating the maintenance of a stem-cell-like state. Moreover, TCR-transgenic and chimeric antigen receptor-modified CD8+ T cells that were expanded with H9T showed robust anti-tumour activity in vivo in mouse models of melanoma and acute lymphoblastic leukaemia. Thus, engineering cytokine variants with distinctive properties is a promising strategy for creating new molecules with translational potential.

Molecular insights into the biased signaling mechanism of the µ-opioid receptor.

GPCR functional selectivity opens new opportunities for the design of safer drugs. Ligands orchestrate GPCR signaling cascades by modulating the receptor conformational landscape. Our study provides insights into the dynamic mechanism enabling opioid ligands to preferentially activate the G protein over the ß-arrestin pathways through the µ-opioid receptor (µOR). We combine functional assays in living cells, solution NMR spectroscopy, and enhanced-sampling molecular dynamic simulations to identify the specific µOR conformations induced by G protein-biased agonists. In particular, we describe the dynamic and allosteric communications between the ligand-binding pocket and the receptor intracellular domains, through conserved motifs in class A GPCRs. Most strikingly, the biased agonists trigger µOR conformational changes in the intracellular loop 1 and helix 8 domains, which may impair ß-arrestin binding or signaling. The findings may apply to other GPCR families and provide key molecular information that could facilitate the design of biased ligands.

High dose antipsychotic polypharmacy and dopamine partial agonists - time to rethink guidelines?

Guidelines for the treatment of schizophrenia limit the use of antipsychotic agents to clinically-established maximum doses. This acknowledges both the absence of additional efficacy of dopamine D2 receptor antagonists above a receptor occupancy threshold, and the increases in side effects that can occur at higher doses. These limits restrict the dosing of combinations of antipsychotics as they do single agents; drugs sharing the major antipsychotic mechanism of D2 receptor antagonism will act additively in blocking these receptors.Several newer antipsychotic drugs, including aripiprazole and cariprazine, act as partial agonists at the D2 receptor site and avoid action at several other receptors, effects at which are responsible for some non-dopaminergic adverse effects. This pharmacology imparts different characteristics to the drugs resulting often in a more favourable side effect profile. Their partial agonism, along with high affinities for the D2 receptor, also means that these drugs given adjunctively may in part replace, rather than enhance, the D2 antagonism of other antipsychotic agents. This can result in an improvement in certain side effects without loss of antipsychotic efficacy.This article makes the case for distinguishing the D2 partial agonists from antagonists in defining maximum doses of combined treatments, which would increase the options available to the prescriber, emphasising that pharmacological mechanisms need to be understood in identifying optimal treatments for psychotic illness.

Partial Agonist Activity of Neonicotinoids on Rat Nicotinic Receptors: Consequences over Epinephrine Secretion and In Vivo Blood Pressure.

Neonicotinoid insecticides are nicotine-derived molecules which exert acute neurotoxic effects over the insect central nervous system by activating nicotinic acetylcholine receptors (nAChRs). However, these receptors are also present in the mammalian central and peripheral nervous system, where the effects of neonicotinoids are faintly known. In mammals, cholinergic synapses are crucial for the control of vascular tone, blood pressure and skeletal muscle contraction. We therefore hypothesized that neonicotinoids could affect cholinergic networks in mammals and sought to highlight functional consequences of acute intoxication in rats with sub-lethal concentrations of the highly used acetamiprid (ACE) and clothianidin (CLO). In this view, we characterized their electrophysiological effects on rat α3ß4 nAChRs, knowing that it is predominantly expressed in ganglia of the vegetative nervous system and the adrenal medulla, which initiates catecholamine secretion. Both molecules exhibited a weak agonist effect on α3ß4 receptors. Accordingly, their influence on epinephrine secretion from rat adrenal glands was also weak at 100 µM, but it was stronger at 500 µM. Challenging ACE or CLO together with nicotine (NIC) ended up with paradoxical effects on secretion. In addition, we measured the rat arterial blood pressure (ABP) in vivo by arterial catheterization. As expected, NIC induced a significant increase in ABP. ACE and CLO did not affect the ABP in the same conditions. However, simultaneous exposure of rats to both NIC and ACE/CLO promoted an increase of ABP and induced a biphasic response. Modeling the interaction of ACE or CLO on α3ß4 nAChR is consistent with a binding site located in the agonist pocket of the receptor. We present a transversal experimental approach of mammal intoxication with neonicotinoids at different scales, including in vitro, ex vivo, in vivo and in silico. It paves the way of the acute and chronic toxicity for this class of insecticides on mammalian organisms.

Combinations of a full and partial agonist: Experimental evidence of curved isoboles.

Concentration addition as a classic null model for toxicology and pharmacology is based on Loewe's mathematical formulation and the linearity of the isoboles. Novel mathematical models, however, propose curved isoboles in certain conditions. This article aims to test the hypothesis of the curvature of isoboles in experimental measurements. With the assumption of linear isoboles, a partial agonist acts as an antagonist above its maximal effect level. The isoboles automatically convert to a positive slope. For curved isoboles, a partial agonist acts as an antagonist at higher effect levels than its maximal effect alone. The discrepancies between effect levels were studied with an estrogen receptor binding assay (BMAEREluc/ERα) using a mixture of 17ß-estradiol and fulvestrant as a partial agonist. A mixture of 17ß-estradiol and fulvestrant acts as a partial agonist and causes the diminishing of the effect level of 17ß-estradiol at a significantly higher level than the maximal effect of their partial-agonistic dose-response curve. Measured, elevated effect levels were well predicted by the mathematical model. Nonlinear isoboles may change our understanding and definition of synergism or antagonism and prompt further attention in receptor theory.

Potent and Subtype-Selective Dopamine D2 Receptor Biased Partial Agonists Discovered via an Ugi-Based Approach.

Using a previously unexplored, efficient, and versatile multicomponent method, we herein report the rapid generation of novel potent and subtype-selective DRD2 biased partial agonists. This strategy exemplifies the search for diverse and previously unexplored moieties for the secondary/allosteric pharmacophore of the common phenyl-piperazine scaffold. The pharmacological characterization of the new compound series led to the identification of several ligands with excellent DRD2 affinity and subtype selectivity and remarkable functional selectivity for either the cAMP (22a and 24d) or the ß-arrestin (27a and 29c) signaling pathways. These results were further interpreted on the basis of molecular models of these ligands in complex with the recent DRD2 crystal structures, highlighting the critical role of the secondary/allosteric pharmacophore in modulating the functional selectivity profile.

Cariprazine as a Treatment Option for Depressive Episodes Associated with Bipolar 1 Disorder in Adults: An Evidence-Based Review of Recent Data.

Depressive episodes, the most frequent episodes in bipolar disorder, contribute in large part to poor functional outcomes. Very few treatments, however, have been approved by the Food and Drug Administration for the treatment of bipolar depression. Cariprazine, a broad-spectrum dopamine antagonist/partial agonist with dopamine D3/D2 (preferring D3) and serotonin 5-HT1A receptor partial agonist properties, was recently approved. A review of the literature suggests that it is an effective and well-tolerated treatment for bipolar depression.

Stable desensitization of α7 nicotinic acetylcholine receptors by NS6740 requires interaction with S36 in the orthosteric agonist binding site.

NS6740 is an α7 nicotinic acetylcholine receptor-selective partial agonist with low efficacy for channel activation, capable of promoting the stable conversion of the receptors to nonconducting (desensitized) states that can be reactivated with the application of positive allosteric modulators (PAMs). In spite of its low efficacy for channel activation, NS6740 is an effective activator of the cholinergic anti-inflammatory pathway. We observed that the concentration-response relationships for channel activation, both when applied alone and when co-applied with the PAM PNU-120596 are inverted-U shaped with inhibitory/desensitizing activities dominant at high concentrations. We evaluated the potential importance of recently identified binding sites for allosteric activators and tested the hypotheses that the stable desensitization produced by NS6740 may be due to binding to these sites. Our experiments were guided by molecular modeling of NS6740 binding to both the allosteric and orthosteric activation sites on the receptor. Our results indicate that with α7C190A mutants, which have compromised orthosteric activation sites, NS6740 may work at the allosteric activation sites to promote transient PAM-dependent currents but not the stable desensitization seen with wild-type α7 receptors. Modeling NS6740 in the orthosteric binding sites identified S36 as an important residue for NS6740 binding and predicted that an S36V mutation would limit NS6740 activity. The efficacy of NS6740 for α7S36V receptors was reduced to zero, and applications of the compound to α7S36V receptors failed to induce the desensitization observed with wild-type receptors. The results indicate that the unique properties of NS6740 are due primarily to binding at the sites for orthosteric agonists.

Ferulic acid alleviates abnormal behaviors in isolation-reared mice via 5-HT1A receptor partial agonist activity.

RATIONALE: Preclinical and clinical reports suggest that ferulic acid (FA), a plant-derived phenylpropanoid, is effective against mental health problems such as agitation, anxiety, and irritability in humans, without causing adverse side effects. However, the mechanism of action is unknown. OBJECTIVE: The aim of the study is to investigate the mechanism underlying the ameliorative effects of FA on mental health problems such as agitation, anxiety, and irritability, using in vivo behavioral analysis, in vitro pharmacological analysis, and in silico binding analysis. METHODS: The effects of FA (10 mg/kg, 50 mg/kg, and 250 mg/kg) on hyperactivity and aggressive behaviors of isolation-reared mice were examined. The effects of FA (50 mg/kg and 250 mg/kg) on extracellular levels of monoamines such as serotonin (5-HT), dopamine, and noradrenaline were analyzed by in vivo microdialysis. The effects of FA (10-13-10-6 M) on 5-HT1A and 5-HT2A receptors were analyzed using a luciferase reporter gene assay. Binding of FA to the mouse 5-HT1A receptor was evaluated by in silico analysis. RESULTS: The behavioral analysis showed that administration of FA (50 mg/kg) 1 h before experiments significantly alleviated hyperactivity and aggressive behaviors in isolation-reared mice. These alleviative effects were abolished by pretreatment with the 5-HT1A receptor antagonist WAY-100635 (1 mg/kg). In vivo microdialysis analysis showed that FA (50 mg/kg) did not change extracellular monoamine levels in the prefrontal cortex of mice. The luciferase reporter gene assay indicated that FA activated 5-HT1A receptors, but not 5-HT2A receptors, in a dose-dependent manner. The maximal response of 5-HT1A receptors to FA was weaker than that to 8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT), a 5-HT1A receptor full agonist. In silico binding analysis showed that FA binds to the orthosteric site of 5-HT1A receptors. CONCLUSION: Taken together, these results suggest that FA ameliorates agitation-, anxiety-, and irritability-like behaviors such as hyperactivity and aggressive behaviors in isolation-reared mice via 5-HT1A receptor partial agonist activity. These findings support the efficacy of FA on mental health problems that have been suggested in preclinical and clinical practice.

Crystal Structure and Subsequent Ligand Design of a Nonriboside Partial Agonist Bound to the Adenosine A2A Receptor.

In this study, we determined the crystal structure of an engineered human adenosine A2A receptor bound to a partial agonist and compared it to structures cocrystallized with either a full agonist or an antagonist/inverse agonist. The interaction between the partial agonist, belonging to a class of dicyanopyridines, and amino acids in the ligand binding pocket inspired us to develop a small library of derivatives and assess their affinity in radioligand binding studies and potency and intrinsic activity in a functional, label-free, intact cell assay. It appeared that some of the derivatives retained the partial agonist profile, whereas other ligands turned into inverse agonists. We rationalized this remarkable behavior with additional computational docking studies.

Human perceptual learning is delayed by the N-methyl-D-aspartate receptor partial agonist D-cycloserine.

BACKGROUND: The optimisation of learning has long been a focus of scientific research, particularly in relation to improving psychological treatment and recovery of brain function. Previously, partial N-methyl-D-aspartate agonists have been shown to augment reward learning, procedural learning and psychological therapy, but many studies also report no impact of these compounds on the same processes. AIMS: Here we investigate whether administration of an N-methyl-D-aspartate partial agonist (D-cycloserine) modulates a previously unexplored process - tactile perceptual learning. Further, we use a longitudinal design to investigate whether N-methyl-D-aspartate-related learning effects vary with time, thereby providing a potentially simple explanation for apparent mixed effects in previous research. METHODS: Thirty-four volunteers were randomised to receive one dose of 250 mg D-cycloserine or placebo 2 h before tactile sensitivity training. Tactile perception was measured using psychophysical methods before and after training, and 24/48 h later. RESULTS: The placebo group showed immediate within-day tactile perception gains, but no further improvements between-days. In contrast, tactile perception remained at baseline on day one in the D-cycloserine group (no within-day learning), but showed significant overnight gains on day two. Both groups were equivalent in tactile perception by the final testing - indicating N-methyl-D-aspartate effects changed the timing, but not the overall amount of tactile learning. CONCLUSIONS: In sum, we provide first evidence for modulation of perceptual learning by administration of a partial N-methyl-D-aspartate agonist. Resolving how the effects of such compounds become apparent over time will assist the optimisation of testing schedules, and may help resolve discrepancies across the learning and cognition domains.

A2A Adenosine Receptor Partial Agonism Related to Structural Rearrangements in an Activation Microswitch.

In drug design, G protein-coupled receptor (GPCR) partial agonists enable one to fine-tune receptor output between basal and maximal signaling levels. Here, we add to the structural basis for rationalizing and monitoring partial agonism. NMR spectroscopy of partial agonist complexes of the A2A adenosine receptor (A2AAR) revealed conformations of the P-I-F activation motif that are distinctly different from full agonist complexes. At the intracellular surface, different conformations of helix VI observed for partial and full agonist complexes manifest a correlation between the efficacy-related structural rearrangement of this activation motif and intracellular signaling to partner proteins. While comparisons of A2AAR in complexes with partial and full agonists with different methods showed close similarity of the global folds, this NMR study now reveals subtle but distinct local structural differences related to partial agonism.

MPL Adjuvant Contains Competitive Antagonists of Human TLR4.

Monophosphoryl lipid A (MPL®) is the first non-alum vaccine adjuvant to achieve widespread clinical and market acceptance, a remarkable achievement given that it is manufactured from a Salmonella enterica endotoxin. To understand how MPL® successfully balanced the dual mandate of vaccine design-low reactogenicity with high efficacy-clinical- and research-grade MPL was evaluated in human and mouse cell systems. Stimulatory dose response curves revealed that most preparations of MPL are much more active in mouse than in human cell systems, and that the limited efficacy observed in human cells correlated with TLR4 inhibitory activity that resulted in a partial agonist profile. Further analysis of the major components of MPL® adjuvant prepared synthetically identified two structural variants that functioned as competitive antagonists of human TLR4. A partial agonist profile could be recapitulated and manipulated by spiking synthetic agonists with synthetic antagonists to achieve a broad dose range over which TLR4 stimulation could be constrained below a desired threshold. This report thus identifies mixed agonist-antagonist activity as an additional mechanism by which MPL® adjuvant is detoxified, relative to its parental LPS, to render it safe for use in prophylactic vaccines.

Pharmacokinetics, safety and metabolite profiling of minesapride, a novel 5-HT4 receptor partial agonist, in healthy elderly and young subjects.

Minesapride is a novel 5-hydroxytryptamine 4 (5-HT4) receptor partial agonist that is expected to show efficacy in patients with irritable bowel syndrome with predominant constipation and functional constipation. An open-label study was conducted to evaluate pharmacokinetics (PK) and safety of minesapride. Japanese subjects, 12 elderly and 12 young, received a single oral dose of minesapride 40 mg/day in the fasted state. Metabolite profiles were also investigated in this clinical study and in an in vitro study using cryopreserved hepatocytes. Clinical results showed that minesapride was rapidly absorbed (Cmax: 2302.1 ng/mL in the elderly group, 2117.5 ng/mL in the young group), and the plasma concentration then decreased with half-life of approximately 7 h. There were no notable PK differences between elderly and young groups. No serious adverse events (AEs) were observed. The only AE that occurred in 2 or more subjects was diarrhea. Metabolite profiles in plasma and urine were similar between elderly and young groups. No major metabolites exceeded 10% of unchanged minesapride, and results of the in vitro study suggested that there were no human-specific metabolites. From the viewpoints of PK and metabolite profiling, no dose adjustment of minesapride is warranted in elderly population without renal or hepatic impairment.

The utilization of buprenorphine in chronic pain.

Reclassification of chronic pain as a disease may be helpful because patients with chronic pain require significant treatment and rehabilitation with a clear diagnosis. This can help address critical factors including suffering, quality of life, participation, and with family and social life, which continue to become more important in evaluating the quality of the health care we give our patients today. During the past decade of the opioid epidemic, methadone was the primary treatment for opioid addiction until buprenorphine was approved. Buprenorphine's high-affinity partial agonist properties make it a good alternative to methadone due to lower abuse potential and safer adverse effect profile while maintaining significant efficacy. Expanded out-patient prescribing options have allowed physician and physician extenders such as physician assistants and nurse practitioners to treat these patients that otherwise would have been required to utilize methadone. With unique pharmacological properties, buprenorphine is a safe and effective analgesic for chronic pain. The literature for buprenorphine shows great potential for its utilization in the treatment of chronic pain.

A comprehensive review of partial opioid agonists for the treatment of chronic pain.

Chronic pain is a common condition that is being increasingly recognized, diagnosed, and treated in a variety of settings. Opioids can be used to treat chronic pain but at the cost of adverse effects and risk of dependence. Recently, there has been a movement to improve analgesic care in the setting of the opioid epidemic and the overprescribing of opioids, causing over-accessibility, dependence, and large numbers of overdose deaths. Opioid-specific receptors, including the µ, δ, κ, and opioid receptor like-1 (ORL-1) receptors, are each 7-transmembrane spanning proteins, which affect the G-protein and ß-arrestin cascades. Each opioid class can act differently on the receptors, resulting in full, partial, or antagonizing effects. This comprehensive review looks at different agents in major classes, nonselective and mixed/partial agonists/antagonists, including the nonselective partial agonists, levorphanol and tramadol. Mixed partial agonists/antagonists include buprenorphine, pentazocine, nalbuphine, and butorphanol. Oliceridine is the only current selective partial agonist that agonizes specific pathways to promote analgesic effects and discourage adverse effects.

Plant-derived natural therapeutics targeting cannabinoid receptors in metabolic syndrome and its complications: A review.

The endocannabinoid system (ECS) is natural physiological system in the humans. The presence of the ECS system involves different roles in body. The endocannabinoid system involves regulation of most of the centers, which regulates the hunger and leads to changes in the weight. In the present article, we reviewed the role of natural cannabinoid compounds in metabolic disorders and related complications. We studied variety of a plant-derived cannabinoids in treating the metabolic syndrome including stoutness, fatty acid liver diseases, insulin obstruction, dementia, hypertension, lipid abnormalities, non-alcoholic steatohepatitis, endothelial damage, and polycystic ovarian syndrome and so on. The activation of cannabinoid receptors demonstrates a significant number of beneficial approaches concerning metabolic syndrome and reduces the pro-inflammatory cytokines on account of aggravation, decreased oxidative stress and uneasiness, diminishes liver fibrosis, with reduces adiponectin. Pre-clinical investigations of plant-derived cannabinoids resulted in promising outcomes. The different distinctive plant-derived cannabinoids were discovered like cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC), and cannabidiol (CBG). It has been observed that endogenous cannabinoids and plant-derived cannabinoids have an advantageous impact on limiting the metabolic disorder arising due to lifestyle changes.

NMDA receptor partial agonist GLYX-13 alleviates chronic stress-induced depression-like behavior through enhancement of AMPA receptor function in the periaqueductal gray.

Depression is a common mental disorder affecting more than 300 million people worldwide and is one of the leading causes of disability among all medical illnesses. The accumulation of preclinical data has fueled the revival of interest in targeting glutamatergic neurotransmission for the treatment of major depressive disorder. GLYX-13, a glutamatergic compound that acts as an N-methyl-d-aspartate (NMDA) modulator with glycine-site partial agonist properties, produces rapid and long-lasting antidepressant effects in both animal models and patients. However, the mechanisms underlying the antidepressant actions of GLYX-13 have not been fully characterized, especially in the midbrain ventrolateral periaqueductal gray (vlPAG), a brain stem area that controls stress-associated depression-like behavior. Here, we use a combination of electrophysiological recordings, behavioral tests, and pharmacological manipulations to study the antidepressant actions of GLYX-13 in the vlPAG. A single intravenous injection of a GLYX-13 rapidly mitigated footshock stress (FS)-induced depression-like behavior in rats. The FS-induced diminished glutamatergic transmission in the vlPAG was also reversed by a single GLYX-13 intravenous injection. Moreover, intra-vlPAG GLYX-13 microinjection produced a long-lasting antidepressant effect; however, this effect was prevented by the intra-vlPAG microinjection of tropomyosin-related kinase B (TrkB) receptor antagonist ANA-12, a selective mammalian target of rapamycin complex 1 (mTORC1) inhibitor rapamycin, and CNQX, an AMPA receptor antagonist. Additionally, a bath application of GLYX-13 enhanced glutamatergic transmission in vlPAG neurons; however, this enhancement effect was blocked by the co-application of ANA-12 and rapamycin. These results demonstrate that BDNF-TrkB-mTORC1 signaling in the vlPAG is required for the sustained antidepressant effects of GLYX-13.