BACKGROUND:Posttraumatic stress disorder (PTSD) is a heterogeneous condition with diverse symptom presentations and emotional experiences. While fear is traditionally viewed as central, growing evidence highlights the role of non-fear-based emotions, such as sadness, guilt, and shame-collectively termed emotional pain. This study aimed to identify fear- and emotional pain-based PTSD symptom profiles and their neural correlates across 2 independent samples. METHODS:In study 1 (N = 838), trauma-exposed individuals with probable PTSD completed the PTSD Checklist for DSM-5 and subjective ratings of fear and emotional pain. Item-level network analysis was conducted to identify central symptoms and relationships. In study 2 (N = 162), recent trauma survivors with high PTSD symptoms underwent resting-state and task-based functional magnetic resonance imaging scans 1 month after trauma and completed follow-up clinical assessment at 14 months after trauma. Connectome-based predictive modeling (CPM) was used to predict chronic symptom severity for fear- and emotional pain-based profiles, identified in study 1. RESULTS:Emotional pain was rated as more impairing than fear by most participants (69%). Symptom networks showed distinct patterns: Fear was associated with flashbacks, nightmares, distressing memories, exaggerated startle, and external avoidance; emotional pain was linked to anhedonia, negative beliefs, negative emotions, sleep disturbance, and emotional reactivity. CPM predicted chronic fear-based symptom severity (ρ = 0.228, p < .001), but not emotional pain (ρ = 0.167, p = .055). Predictive features included connections across anterior default mode, central executive, salience, motor-sensory, and subcortical networks. CONCLUSIONS:Emotional pain and fear may represent distinct PTSD dimensions. Disentangling their neural signatures may improve diagnostic precision and guide personalized, mechanism-based interventions for trauma-related psychopathology.

Objective: To assess proof-of-concept (PoC) for efficacy, tolerability, and safety of TRPC4/5 inhibitor BI 1358894 vs placebo in patients with major depressive disorder (MDD) with inadequate response to ongoing antidepressants. Methods: In this phase 2, multicenter, randomized, double-blind, dose-finding trial (December 2020-February 2024), patients with MDD (per DSM-5) and current depressive episode of ≥8 weeks and ≤24 months were randomized (3.5:1:1:1:2:2) to receive placebo or BI 1358894 (5 mg, 25 mg, 75 mg, or 125 mg) or quetiapine 150-300 mg orally, once daily for 6 weeks. Primary end point was change from baseline in Montgomery-Åsberg Depression Rating Scale (MADRS) total score at Week 6. Secondary end points included ≥50% reduction from baseline in MADRS total score at Week 6, change from baseline in State-Trait Anxiety Inventory scores, Clinical Global Impression Severity Scale score, and Symptoms of Major Depressive Disorder Scale total score at Week 6. Results: Of 940 enrolled patients, 389 were randomized, and 361 (93.0%) completed the trial. No differences were observed between BI 1358894 treatment groups and placebo for primary and secondary end points. Adverse events were slightly more frequent in the BI 1358894-total group (66.7%) vs placebo (53.9%). No worsening of Columbia-Suicide Severity Rating Scale was observed for most patients; serious adverse events of suicidal ideation were reported for 4.7% (placebo), 5.1% (BI 1358894 75 mg group), and 1.4% (quetiapine) of patients. Conclusion: Although this was a negative trial in MDD with PoC not established, BI 1358894 was well tolerated with no increase in self-harm or suicidality. Trial Registration: ClinicalTrials.gov identifier: NCT04521478.

BACKGROUND AND PURPOSE:Pharmacological inhibition of TRPC4 and/or TRPC5 channels reduces Pavlovian aversion memory in stressed mice and reduces amygdala reactivity to aversion in humans with depression. The aims of this mouse study were to improve understanding of these anxiolytic processes, determine whether there are corrective effects on reward processes, and provide further translational evidence for TRPC4/C5 channel brain and neuron distribution. EXPERIMENTAL APPROACH:Mouse models of chronic social stress (CSS), with increased aversion and decreased reward responding, were applied to investigate the effects of a TRPC4/TRPC5 channel inhibitor. RT-qPCR and FISH were used to determine regional and neuronal gene expression. KEY RESULTS:Male mice underwent CSS, or were controls, and a TRPC4/TRPC5 inhibitor or vehicle was administered prior to Pavlovian aversion learning: stressed-vehicle mice displayed excessive Pavlovian learning, measured as high freezing to tone and context, and this was reduced by a TRPC4/TRPC5 inhibitor. Different stressed and control mice were tested on discriminative reward learning: there was no TRPC4/TRPC5 inhibitor effect on learning, but it did increase reward responding and effortful reward motivation in stressed mice. In naive male and female mice, Trpc4 and Trpc5 gene levels were moderate and high in glutamate principal neurons in basolateral amygdala and ventral hippocampus, respectively; co-expression with the CCKB receptor was substantial. TRPC4 and TRPC5 were expressed by glutamate neurons in human amygdala and hippocampus. CONCLUSIONS AND IMPLICATIONS:This study furthers understanding of the therapeutic potential of TRPC4/TRPC5 channel inhibition for excessive aversion processing and impaired reward processing.

The RDoC framework focuses on neurobehavioral processes often dysfunctional in mental disorders and commensurate with translational research. Generalized hyper-sensitivity to aversion/threat is common in various stress-related emotional disorders; increased Pavlovian aversion learning-memory (PAL, PAM) provides a translational paradigm for its study. Here we present the development and application of a mouse model for the study of generalized hyper-sensitivity to aversion/threat. In male adult mice, chronic exposure to social aversion (chronic social stress, CSS) leads, relative to controls (CON), to increased acquisition and expression of tone-footshock conditioned freezing behavior. The altered neurobehavioral state of CSS mice is expected to involve structure-function changes in amygdala: in CSS mice, higher levels of both PAL and PAM freezing behavior co-occurred with fewer lateral/basal amygdala glutamate neurons expressing the immediate early-gene protein c-Fos. A current antidepressant, SSRI escitalopram, reversed excessive PAM freezing behavior in CSS mice with sub-chronic dosing. The model was applied to investigate 3 compounds with novel mechanisms of action: indoleamine dioxygenase 1 (IDO 1) inhibition, somatostatin receptor 4 (SSTR4) agonism, and transient receptor potential canonical channels 4 and 5 (TRPC4/5) inhibition. For each, there was evidence for attenuation of excessive PAL and/or PAM in CSS mice. Preclinical validation of TRPC4/5 channels inhibition contributed to the decision to investigate, and accurately predicted, clinical efficacy, measured as reduced amygdala and emotional reactivities to aversion in major depressive disorder. Future work will focus on (back-)translational studies that address stress-induced changes in amygdala reactivity and aversion processing, their underlying etio-pathophysiological causes, and neuropharmacological responsiveness.

Transient receptor potential canonical (TRPC) ion channels are expressed in areas of the brain responsible for processing emotion and mood and have been implicated in the pathophysiology of internalizing disorders such as major depressive disorder and anxiety disorders. This review outlines the rationale for targeting TRPC ion channels for drug development, with specific focus on TRPC4 and TRPC5. We provide preclinical evidence that the lack of TRPC4 and TRPC5 channels or its pharmacological inhibition attenuate fear and anxiety without impairing other behaviors in mice. We also report on clinical studies of BI 1358894, a small molecule inhibitor of TRPC4/5 ion channels, demonstrating reduced psychological and physiological responses to induced anxiety/panic-like symptoms in healthy volunteers. Furthermore, we highlight an imaging study that investigated the acute effects of BI 1358894 and showed reduced activation in several brain regions involved in emotional processing. We conclude that these findings demonstrate a critical role for TRPC4 and TRPC5 in emotional processing, even though it remains an open question if the biological signatures of TRPC4/5 inhibition reported here translate into clinical efficacy and indicate that a TRPC4/5 inhibitor might provide a more effective treatment of internalizing disorders.

INTRODUCTION:Depression, anxiety, and/or panic disorder are often comorbid and have a complex etiology mediated through the same neuronal network. Cholecystokinin-tetrapeptide (CCK-4), a synthetic analog of the endogenous neuropeptide cholecystokinin (CCK), is thought to be implicated in this network. The CCK-4 challenge model is an accepted method of investigating the pathophysiology of panic and has been shown to mediate neuronal activation via the transient receptor potential canonical (TRPC) ion channels.OBJECTIVES:This study aimed to assess the pharmacodynamic effects of BI 1358894, a small-molecule inhibitor of TRPC ion channel members 4 and 5 (TRPC4/5), on CCK-4-induced anxiety/panic-like symptoms and evaluate circuit engagement.METHODS:Twenty healthy male CCK-4-sensitive volunteers entered a Phase I, double blind, randomized, two-way cross-over, single dose, placebo-controlled trial. Randomization was to oral BI 1358894 100 mg in the fed state followed by oral placebo in the fed state, or vice versa. Treatments were administered 5 h prior to intravenous CCK-4 50 µg. The primary endpoint was maximum change from baseline of the Panic Symptom Scale (PSS) sum intensity score after CCK-4 injection. Further endpoints included the emotional faces visual analog score (EVAS), the Spielberger State-Trait Anxiety Inventory (STAI), plasma adrenocorticotropic hormone (ACTH), and serum cortisol values. The safety and tolerability of BI 1358894 was assessed based on a number of parameters including occurrence of adverse events (AEs). All pharmacodynamic, pharmacokinetic, and safety endpoints were analyzed using descriptive statistics.RESULTS:Single oral doses of BI 1358894 were generally well tolerated by the healthy male volunteers included in this study. Adjusted mean maximum change from baseline in PSS sum intensity score was 24.4 % lower in volunteers treated with BI 1358894 versus placebo, while adjusted mean maximum change from baseline of EVAS was reduced by 19.2 % (BI 1358894 vs placebo). The STAI total score before CCK-4 injection was similar in both groups (placebo: 25.1; BI 1358894: 24.3). Relative to placebo, BI 1358894 reduced CCK-4-induced mean maximum plasma ACTH and serum cortisol values by 58.6 % and 27.3 %, respectively. Investigator-assessed drug-related AEs were reported for 13/20 participants (65.0 %). There were no serious or severe AEs, AEs of special interest, AEs leading to discontinuation of trial medication, or deaths.CONCLUSIONS:Overall, BI 1358894 reduced psychological and physiological responses to CCK-4 compared with placebo, as measured by PSS, subjective EVAS and objectively measured stress biomarkers. BI 1358894 had a positive safety profile, and single oral doses were well tolerated by the healthy volunteers. This trial (NCT03904576/1402-0005) was registered on Clinicaltrials.gov on 05.04.19.

BI 1569912 is a negative allosteric modulator of NR2B subunit-containing N-methyl-D-aspartate (NMDA) receptors, under development as a treatment for major depressive disorder. Safety, tolerability and food-dependent bioavailability were investigated in a Phase I study conducted at a single site in Germany (Charité, Berlin). Electroencephalography (EEG) and eye-tracking were measured as treatment-response biomarkers to evaluate central target engagement by BI 1569912.

Abnormal emotional processing in major depressive disorder (MDD) has been associated with increased activation to negative stimuli in cortico-limbic brain regions. The authors investigated whether treatment with BI 1358894, a small-molecule inhibitor of the transient receptor potential cation channel subfamily C leads to attenuated activity in these areas in MDD patients. 73 MDD patients were randomized to receive a single oral dose of BI 1358894 (100 mg), citalopram (20 mg), or matching placebo. Brain responses to emotional faces and scenes were investigated using functional magnetic resonance imaging. Primary endpoints were BOLD signal changes in response to negative faces in cortico-limbic brain regions, i.e. bilateral amygdala (AMY), dorsolateral prefrontal cortex, anterior insula (AI), and anterior cingulate cortex. Secondary endpoints were BOLD signal changes in response to negative scenes. For each region, separate ANOVA models were computed for the comparison of treatments (BI 1358894 or citalopram) vs. placebo. The adjusted treatment differences in the % BOLD signal changes in the faces task showed that BI 1358894 induced signal reduction in bilateral AMY and left AI. In the scenes task, BI 1358894 demonstrated significant signal reduction in bilateral AMY, AI, anterior cingulate cortex and left dorsolateral prefrontal cortex. Citalopram failed to induce any significant reductions in BOLD signal in both tasks. BI 1358894-mediated inhibition of the transient receptor potential cation channel subfamily resulted in strong signal reduction in cortico-limbic brain regions, thereby supporting development of this mechanism of action for MDD patients.

BACKGROUND: Excessive processing of aversive life events is a major pathology in stress-related anxiety and depressive disorders. Current pharmacological treatments have rather nonspecific mechanisms of action. Somatostatin is synthesized and released as an inhibitory co-neurotransmitter by specific GABA (gammaaminobutyric acid) interneurons, and one of its receptors, SSTR4 (somatostatin receptor 4), is localized in brain regions involved in adaptive aversion processing and implicated in negative valence neuropathology, including the amygdala.METHODS: Rat and mouse experiments were conducted to investigate effects of specific SSTR4 agonism on neurobehavioral aversion processing, including any normalization of stress-related hyperresponsiveness. A mouse experiment to investigate stress and SSTR4 agonism effects on reward processing was also conducted. RESULTS: In male rats (n = 5-10/group) fitted with glutamate biosensors in basolateral amygdala, SSTR4 agonism attenuated glutamate release to restraint stress in control rats and particularly in rats previously exposed to chronic corticosterone. In male mice (n = 10-18/group), SSTR4 agonism dose-dependently attenuated Pavlovian tone/ footshock learning and memory measured as freezing behavior, in both control mice and mice exposed to chronic social stress, which induces excessive Pavlovian aversion learning and memory. Specificity of SSTR4 agonism effects to aversion learning/memory was demonstrated by absence of effects on discriminative reward (sucrose) learning/memory in both control mice and mice exposed to chronic social stress; SSTR4 agonism did increase reward-to-effort valuation in a dose-dependent manner and in both control mice and mice exposed to chronic social stress, which attenuates reward motivation.CONCLUSIONS: These neuropsychopharmacological findings add substantially to the preclinical proof-of-concept evidence for SSTR4 agonism as a treatment in anxiety and depressive disorders.

The non-selective NMDA-receptor blockers ketamine and esketamine have been demonstrated efficacy in multiple clinical trials in patients with major depressive disorder (MDD). The use of those substances is limited due to high probability of psychotomimetic-like effects. The NR2B subunit is considered key in mediating the efficacy of ketamine. BI 1569912 is a novel negative allosteric modulator of NR2B-containing NMDA receptors under development for the treatment of MDD.

BACKGROUND:Forty million adults in the US suffer from anxiety disorders, making these the most common forms of mental illness. Transient receptor potential channel canonical subfamily (TRPC) members 4 and 5 are non-selective cation channels highly expressed in regions of the cortex and amygdala, areas thought to be important in regulating anxiety. Previous work with null mice suggests that inhibition of TRPC4 and TRPC5 may have anxiolytic effects.HC-070 IN VITRO:To assess the potential of TRPC4/5 inhibitors as an avenue for treatment, we invented a highly potent, small molecule antagonist of TRPC4 and TRPC5 which we call HC-070. HC-070 inhibits recombinant TRPC4 and TRPC5 homomultimers in heterologous expression systems with nanomolar potency. It also inhibits TRPC1/5 and TRPC1/4 heteromultimers with similar potency and reduces responses evoked by cholecystokinin tetrapeptide (CCK-4) in the amygdala. The compound is >400-fold selective over a wide range of molecular targets including ion channels, receptors, and kinases.HC-070 IN VIVO:Upon oral dosing in mice, HC-070 achieves exposure levels in the brain and plasma deemed sufficient to test behavioral activity. Treatment with HC-070 attenuates the anxiogenic effect of CCK-4 in the elevated plus maze (EPM). The compound recapitulates the phenotype observed in both null TRPC4 and TRPC5 mice in a standard EPM. Anxiolytic and anti-depressant effects of HC-070 are also observed in pharmacological in vivo tests including marble burying, tail suspension and forced swim. Furthermore, HC-070 ameliorates the increased fear memory induced by chronic social stress. A careful evaluation of the pharmacokinetic-pharmacodynamic relationship reveals that substantial efficacy is observed at unbound brain levels similar to, or even lower than, the 50% inhibitory concentration (IC50) recorded in vitro, increasing confidence that the observed effects are indeed mediated by TRPC4 and/or TRPC5 inhibition. Together, this experimental data set introduces a novel, high quality, small molecule antagonist of TRPC4 and TRPC5 containing channels and supports the targeting of TRPC4 and TRPC5 channels as a new mechanism of action for the treatment of psychiatric symptoms.

GABAergic inhibition is essential for normal cortical function as it serves the purpose of proper excitation/inhibition (E/I) balance in many circuits. In contrast, inappropriate interneuron signaling leads to E/I imbalance, reduced gamma oscillations in EEG measurements and has serious behavioural consequences. Among the heterogeneous group of GABAergic cells, fast-spiking, parvalbumin positive interneurons (FS-PV+) play a key role in the generation and maintenance of gamma oscillations. E/I imbalance due to interneuron dysfunction has been implicated in the pathophysiology of various psychiatric disorders. Cognitive impairment has been associated with altered gamma oscillation in schizophrenia and there is accumulating evidence for involvement of FS-PV+ interneuron deficit in the disease. Hypofunction of FS-PV+ neurons leads to disinhibition of pyramidal cells which cause network desynchronization. Therefore, it is hypothesized that activation of these neurons could restore high-frequency oscillations and consequently improve cognitive functions. However selective modulation of different interneuron types is still challenging due to limited number of known cell type specific targets. A possible starting point for the treatment could be pharmacological activation of voltage gated sodium channels (Nav) which have a pivotal role in action potential initiation. Of the four subtypes of Nav channels expressed in the CNS Nav 1.1 comprises the majority of the sodium current in FS-PV+ but not in pyramidal neurons. Based on this we looked for selective Nav 1.1 activators and found a recently published promising compound (Compound 3a, see Crestey et al, 2015) which has been shown to increase the electrical activity of FS-PV+ interneurons in the CA1 area of the hippocampus. However, the dysfunction in information processing found in schizophrenic patients is not only restricted to the hippocampus and high-order association cortices but also influences the sensory cortex. Thus, our aim was to explore the effect of the selective Nav 1.1 positive modulator Compound 3a on FS interneurons in the mouse somatosensory cortex. We performed whole-cell patch clamp recordings from mouse cortical brain slices and recorded the electrical activity of single FS cells before and after the drug application. Surprisingly the excitatory effect of the compound 3a could only partly be confirmed in the way that positive modulation of Nav1.1 in terms of action potential number and threshold only takes place under particular conditions, i.e. at physiological temperature and under specific ion compositions of the recording solutions The discrepancy of our results from published data might be attributed to the different experimental conditions such as recording temperature and ionic composition of solutions and highlight the importance of selecting near physiological conditions during brain slice patch clamp experiments.

Somatostatin (SST) is a peptide hormone that regulates the endocrine system and affects neurotransmission via interaction with G protein-coupled SST receptors and inhibition of the release of different hormones. The aim of this study was to investigate whether the analgesic properties of the selective SSTR4 agonist J-2156 are mediated via peripheral and/or spinal receptors. Effect on mechanical hyperalgesia in the Complete Freund׳s Adjuvant (CFA) model was measured after intraperitoneal application of J-2156. Electrophysiological neuronal recordings were conducted 24 h after injection of CFA or vehicle into the paw of Wistar rats. Mechanosensitivity of peripheral afferents of the saphenous nerve as well as of spinal wide dynamic range (WDR) and nociceptive-specific (NS) neurons were measured after systemic or spinal application of J-2156. In CFA animals J-2156 dose dependently reduced hyperalgesia in behavioral studies. The minimal effective dose was 0.1 mg/kg. Mechanosensitivity of peripheral afferents and spinal neurons was significantly reduced by J-2156. NS neurons were dose dependently inhibited by J-2156 while in WDR neurons only the highest concentration of 100 µM had an effect. In sham controls, J-2156 had no effect on neuronal activity. We demonstrated that J-2156 dose-dependently reduces peripheral and spinal neuronal excitability in the CFA rat model without affecting physiological pain transmission. Given the high concentration of the compound required to inhibit spinal neurons, it is unlikely that the behavioral effect seen in CFA model is mediated centrally. Overall these data demonstrated that the analgesic effect of J-2156 is mediated mainly via peripheral SST4 receptors.

Somatostatin (sst) is a cyclic neuropeptide known to have inhibitory roles in the central nervous system. It exerts its biological effects via the activation of the 5 sst receptor subtypes, which belong to the family of G-protein coupled receptors (GPCR). This peptide has analgesic properties, specifically via the activation of the sst4 receptor subtype. Although this is established, the precise molecular mechanisms causing this have not yet been fully elucidated. This research aimed to identify a possible anti-nociceptive mechanism, showing functional links to the transient receptor potential vanilloid type 1 (TRPV1) within the pain processing pathway. Calcium imaging and whole cell voltage clamp experiments were conducted on DRG neurons prepared from adult rats, utilizing capsaicin stimulations and the sst4 receptor specific agonist J-2156. The complete Freund's adjuvant (CFA) inflammatory pain model was used to examine if effects are augmented in pain conditions. The sst4 receptor agonist J-2156 was able significantly to inhibit capsaicin induced calcium and sodium influx, where the effect was more potent after CFA treatment. This inhibition identifies a contributory molecular mechanism to the analgesic properties of sst4 receptor activation.

Somatostatin has a wide biological profile resulting from its actions on the five receptor subtypes (sst1-5). Recently somatostatin was shown to exert analgesic effects via activation of the sst4 receptor. Although the analgesia in pain models is established, the precise molecular mechanism has yet to be fully elucidated. This research aimed to identify possible anti-nociceptive mechanisms, showing functional links of the sst4 receptor to G-protein coupled inward rectifying potassium (GIRK) channels and reduction of voltage stimulated calcium influx within the pain processing pathway. Whole cell voltage clamp experiments and calcium imaging experiments were conducted on DRG neurons prepared from adult rats. Application of an sst4 receptor selective agonist, J-2156, on DRG neurons induced a GIRK modulated potassium current, and inhibited voltage sensitive calcium current. Both mechanisms are thought to contribute to the analgesic properties of sst4 receptor agonists.

Abstract Although the so-called triptans are efficacious and are generally well-tolerated drugs for the treatment of migraine headache, there is still a need for improvement of migraine therapy. The relatively low number of patients becoming pain free in addition to the relatively high number of patients experiencing a recurrence of headache and lacking consistency of relief, together with the potential for cardio vascular adverse effects, reflect the limitations of the triptans as the present therapeutic standards. Since the introduction of triptans to the market, several other treatment approaches targeting different aspects of migraine pathogenesis have reached clinical status, but most of them failed or showed no real therapeutic advantage.

Calcitonin gene-related peptide (CGRP) is known to play a major role in the pathogenesis of pain syndromes, in particular migraine pain. Here we focus on its implication in a rat pain model of inflammation, induced by injection of complete Freund adjuvant (CFA). The nonpeptide CGRP receptor antagonist BIBN4096BS reduces migraine pain and trigeminal neuronal activity. Here we demonstrate that the compound reduces inflammatory pain and spinal neuronal activity. Behavioural experiments reveal a reversal of the CFA-induced mechanical hypersensitivity and monoiodoacetate (MIA)-induced weight-bearing deficit in rats after systemic drug administration. To further investigate the mechanism of action of the CGRP antagonist in inflammatory pain, in vivo electrophysiological studies were performed in CFA-injected rats. Recordings from wide dynamic range neurons in deep dorsal horn layers of the lumbar spinal cord confirmed a reduction of neuronal activity after systemic drug application. The same amount of reduction occurred after topical administration onto the paw, with resulting systemic plasma concentrations in the low nanomolar range. However, spinal administration of BIBN4096BS did not modify the neuronal activity in the CFA model. Peripheral blockade of CGRP receptors by BIBN4096BS significantly alleviates inflammatory pain. (C) 2013 International Association for the Study of Pain. Published by Elsevier B. V. All rights reserved.