Biology subjects

Mennerick, S.

Publications and source records attributed to Mennerick, S..

10 recordsLinked to original sources

bioRxiv2026

Targeting Histamine H3 Receptors to Suppress NGF-Driven Hyperexcitability in Neuropathic Pain

Peripheral nerve injury induces long-lasting changes in sensory neurons that contribute to the development of neuropathic pain. Although the histamine H3 receptor (H3R) is best known for regulating neurotransmitter release in the central nervous system, its expression and role in dorsal root ganglia (DRG) remain poorly understood. In this study, we examined the expression, cellular distribution, and functional role of H3 R in DRG and implications in neuropathic pain. Sciatic nerve injury increased membrane-associated H3R protein expression in the DRG, suggesting enhanced receptor trafficking or stabilization at the neuronal membrane. Single-cell transcriptomic analysis revealed that H3R mRNA expression in DRG is predominantly restricted in peptidergic sensory neurons and C-LTMRs neurons. Fluorescence imaging and transcriptomic analysis also suggest that the majority of H3R co-express with TrkA (a NGF receptor) sensory neuron populations. These findings identify a subset of NGF-responsive nociceptors in which H3R may directly influence injury-induced sensitization. Pain behavior assessment demonstrated a paradoxical role of an H3R inverse agonist (GSK334429), which reduces mechanical hypersensitivity caused by chronic constriction injury (CCI) with no change in thermal pain. Patch-clamp recordings show that the GSK334429 attenuates NGF-induced hyperexcitability in DRG neuronal cultures. Overall, our work suggests a contributing role of H3R in modality-specific effects on sensory processing through its enrichment in specific neuronal populations in DRG.

neuroscience↗

bioRxiv2026

A Non-Classical Neuroactive Steroid Exhibiting Potent, Efficacious GABA A Receptor Agonism and NMDA Receptor Inhibition

Neuroactive steroids modulate GABAA and NMDA receptors allosterically, typically requiring specific structural features for their activity. In this study, we characterize YX84, a novel neuroactive steroid bearing a 3{beta} sulfate and p-trifluoroacetylbenzyl alcohol attached in an ether linkage to a hydroxyl group at steroid carbon 17. This compound and similar analogues exhibit an atypical pharmacological profile, with three distinct actions at GABAA receptors. First, YX84 is a full agonist, with EC50 near 1 {micro}M and comparable efficacy to GABA at GABAA receptors in native hippocampal neurons. It presents as a full agonist relative to GABA at 4/{delta} subunit-containing receptors. Second, YX84 acts as a slow-onset, potent positive allosteric modulator (PAM) of GABAA receptors at concentrations below those that gate a response. Finally, YX84 exhibits rapid desensitizing and/or blocking kinetics; voltage dependence is consistent with a contribution of channel block. Structure- activity relationship analyses reveal that both functional groups are essential for gating activity, while classical requirements such as carbon 3 hydroxyl stereoselectivity and carbon 5 reduction are dispensable. YX84 also modestly inhibits NMDA receptor currents, suggesting weak negative allosteric modulation. Behavioral assays show that intraperitoneal administration of YX84 (30 mg/kg) does not impair sensorimotor function, unlike allopregnanolone. These findings identify YX84 as a structurally distinct neuroactive steroid with dual receptor activity and favorable behavioral tolerability, offering a promising scaffold for therapeutic development targeting excitatory/inhibitory imbalance in neuropsychiatric disorders if pharmacokinetic considerations can be overcome.

neuroscience↗

bioRxiv2026

Subunit selective modulation of GABAA receptors using pharmacogenetically tethered neurosteroids

Neurosteroids are powerful endogenous modulators of inhibition and emerging therapeutics for anxiety, epilepsy, and mood disorders, yet their actions at defined receptor subtypes and within specific neuronal populations remain poorly resolved. Here, we engineer a neurosteroid DART (Drug Acutely Restricted by Tethering) platform to deliver neuroactive steroid (NAS) activity with cellular precision and receptor-subunit selectivity. From a screen of seventeen NAS analogs, we identified seven scaffolds suitable for further engineering, and we discovered that linker attachment at the steroid C11 position uniquely preserves NAS positive allosteric modulation of GABAA receptors, whereas C2 and C17 attachment abolished activity. C11-linked NAS-DARTs slowed IPSC decay kinetics and showed variable off-target modulation of NMDA and AMPA EPSCs. The lead DART compound, YX85.1DART.2, enhanced GABA-evoked currents in neurons expressing engineered 4/{delta}-containing GABAA receptors but spared {gamma}2-containing receptors. A complementary benzodiazepine DART BZP.1DART.2 showed the opposite selectivity. Together, these tools enable cell-restricted, subunit-resolved interrogation of neurosteroid action on inhibitory microcircuits and provide a strategy to dissect how distinct GABAA receptor subclasses contribute to circuit function and therapeutic outcomes.

neuroscience↗

bioRxiv2025

VDAC activation inhibits hippocampal plasticity via NLRP3 inflammasome & caspase-1: modulation by allopregnanolone enantiomers

Voltage-dependent anion channels (VDACs) are the most abundant proteins in the outer mitochondrial membrane (OMM) and key regulators of mitochondrial function under physiological and pathological conditions. These channels are modulated by multiple agents and are known binding sites for neuroactive steroids (NAS) including allopregnanolone (AlloP). Using erastin, an agent that promotes VDAC activation by preventing inhibition by tubulin, we assessed the impact of VDAC activation on hippocampal function. Brief erastin administration had no effect on basal transmission but completely inhibited induction of long-term potentiation (LTP) in the Schaffer collateral pathway of rat hippocampal slices. This LTP inhibition was prevented by VBIT-4, an agent that inhibits VDAC oligomerization. VDAC-mediated LTP inhibition was also prevented by inhibitors of the NLRP3 inflammasome and caspase-1, downstream effectors of VDACs, but not by inhibition of cGAS-STING, narrowing the neuroinflammatory pathways involved. Similarly, effects of erastin were prevented by AlloP and at lower concentrations by its unnatural enantiomer (ent-AlloP), an agent that unlike AlloP has little effect on GABAA receptors. Erastin also inhibited memory formation in a hippocampal-dependent form of one-trial learning and these effects were prevented by VBIT-4 and ent-AlloP, but not by a non-sedating dose of AlloP. These results have relevance for understanding the role of VDACs as mediators of neuronal stress and for the further development of NAS as neurotherapeutics and modulators of cellular stress. SIGNIFICANCE STATEMENTVoltage-dependent anion channels (VDACs) are important regulators of mitochondrial function, playing roles in cellular metabolism, stress responses and neuroinflammation, and contribute to the pathogenesis of neuropsychiatric illnesses. Here we show that erastin, an agent that activates VDACs initiates specific neuroinflammatory responses to acutely disrupt synaptic plasticity in the rodent hippocampus and abrogate learning. These adverse effects are prevented by the neuroactive steroids allopregnanolone, which binds VDACs and is used clinically for postpartum depression, and its unnatural enantiomer, suggesting that these agents could have therapeutic effects in a broad range of brain illnesses.

neuroscience↗

bioRxiv2025

Multifaceted Actions of Neurosteroids

Background and purposeNeurosteroids modulate neuronal function and are promising therapeutic agents for neuropsychiatric disorders. Neurosteroid analogues are approved for treating postpartum depression and are of interest in other disorders. GABA-A receptors are well characterized targets of natural neurosteroids, but other biological pathways are likely relevant to therapeutic mechanisms and/or to off-target effects. We performed hypothesis-generating in silico analyses and broad in vitro biological screens to assess the range of actions of neurosteroids analogues of varying structural attributes. Key ResultsWe employed in silico molecular similarity analysis and network pharmacology to elucidate likely targets. This analysis confirmed likely targets beyond GABA-A receptors. We then functionally screened 19 distinct neurosteroid structures across 78 targets representing interconnected signaling pathways, complemented with a limited screen of kinase activation. Results revealed unanticipated modulation of targets by neurosteroids with some structural selectivity. Many compounds-initiated androgen receptor translocation with little or no enantioselectivity. Modulation of multiple G-protein receptors was also unexpected. Conclusions and implicationsNeurosteroids are ascendant treatments in neuropsychiatry, but their full spectrum of actions remains unclear. This virtual and biological screening discovery approach opens new vistas for exploring mechanism of neurosteroids analogues. The multifaceted approach provides an unbiased, holistic exploration of the potential effects of neurosteroids across various molecular targets and provides a platform for future validation studies to aid drug discovery.

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bioRxiv2024

δ-containing GABAA receptors on parvalbumin interneurons modulate neuronal excitability and network dynamics in the mouse medial prefrontal cortex

In medial prefrontal cortex (mPFC), fast-spiking parvalbumin (PV) interneurons regulate excitability and microcircuit oscillatory activity important for cognition. Although PV interneurons inhibit pyramidal neurons, they themselves express {delta} subunits of GABAA receptors important for slow inhibition. However, the specific contribution of {delta}-containing GABAA receptors to the function of PV interneurons in mPFC is unclear. We explored cellular, synaptic, and local-circuit activity in PV interneurons and pyramidal neurons in mouse mPFC after selectively deleting {delta} subunits in PV interneurons (cKO mice). In current-clamp recordings, cKO PV interneurons exhibited a higher frequency of action potentials and higher input resistance than wild type (WT) PV interneurons. Picrotoxin increased firing and GABA decreased firing in WT PV interneurons but not in cKO PV interneurons. The {delta}-preferring agonist THIP reduced spontaneous inhibitory postsynaptic currents in WT pyramidal neurons but not in cKO pyramidal neurons. In WT slices, depolarizing the network with 400 nM kainate increased firing of pyramidal neurons but had little effect on PV interneuron firing. By contrast, in cKO slices kainate recruited PV interneurons at the expense of pyramidal neurons. At the population level, kainate induced broadband increases in local field potentials in WT but not cKO slices. These results on cells and the network can be understood through increased excitability of cKO PV interneurons. In summary, our study demonstrates that {delta}-containing GABAA receptors in mPFC PV interneurons play a crucial role in regulating their excitability and the phasic inhibition of pyramidal neurons, elucidating intricate mechanisms governing cortical circuitry. Significance statementBy selectively deleting {delta}-containing GABAA receptors in PV interneurons, we demonstrate the importance of these receptors on PV interneuron excitability, synaptic inhibition of pyramidal neurons, and circuit function.

neuroscience↗

bioRxiv2024

A role for δ subunit-containing GABA-A receptors on parvalbumin positive neurons in maintaining electrocortical signatures of sleep states

GABAA receptors containing {delta} subunits have been shown to mediate tonic/slow inhibition in the CNS. These receptors are typically found extrasynaptically and are activated by relatively low levels of ambient GABA in the extracellular space. In the mouse neocortex, {delta} subunits are expressed on the surface of some pyramidal cells as well as on parvalbumin positive (PV+) interneurons. An important function of PV+ interneurons is the organization of coordinated network activity that can be measured by EEG; however, it remains unclear what role tonic/slow inhibitory control of PV+ neurons may play in shaping oscillatory activity. After confirming a loss of functional {delta} mediated tonic currents in PV cells in cortical slices from mice lacking Gabrd in PV+ neurons (PV {delta}cKO), we performed EEG recordings to survey network activity across wake and sleep states. PV {delta}cKO mice showed altered spectral content of EEG during NREM and REM sleep that was a result of increased oscillatory activity in NREM and the emergence of transient high amplitude bursts of theta frequency activity during REM. Viral reintroduction of Gabrd to PV+ interneurons in PV {delta}cKO mice rescued REM EEG phenotypes, supporting an important role for {delta} subunit mediated inhibition of PV+ interneurons for maintaining normal REM cortical oscillations. Significance statementThe impact on cortical EEG of inhibition on PV+ neurons was studied by deleting a GABAA receptor subunit selectively from these neurons. We discovered unexpected changes at low frequencies during sleep that were rescued by viral reintroduction.

neuroscience↗

bioRxiv2024

Sertraline modulates hippocampal plasticity and learning via sigma 1 receptors, cellular stress and neurosteroids

In addition to modulating serotonin transport, selective serotonin reuptake inhibitors (SSRIs) have multiple other effects that may contribute to clinical effects, and some of these latter actions prompt repurposing of SSRIs for non-psychiatric indications. We recently observed that the SSRIs fluvoxamine and fluoxetine prevent the acute adverse effects of pro-inflammatory stimulation on long-term potentiation (LTP) in the CA1 hippocampal region. Sertraline showed markedly different effects, acutely inhibiting LTP at a low micromolar concentration through inverse agonism of sigma 1 receptors (S1Rs). In the present studies, we pursued mechanisms contributing to sertraline modulation of LTP in rat hippocampal slices. We found that sertraline partially inhibits synaptic responses mediated by N-methyl-D-aspartate receptors (NMDARs) via effects on NMDARs that express GluN2B subunits. A selective S1R antagonist (NE-100), but not an S1R agonist (PRE-084) blocked effects on NMDARs, despite the fact that both S1R ligands were previously shown to prevent LTP inhibition. Both NE-100 and PRE-084, however, prevented adverse effects of sertraline on one-trial learning. Because of the important role that S1Rs play in modulating endoplasmic reticulum stress, we examined whether inhibitors of cellular stress alter effects of sertraline. We found that two stress inhibitors, ISRIB and quercetin, prevented LTP inhibition, as did inhibitors of the synthesis of endogenous neurosteroids, which are homeostatic regulators of cellular stress. These studies highlight complex effects of sertraline, S1Rs and neurosteroids on hippocampal function and have relevance for understanding therapeutic and adverse drug actions.

neuroscience↗

bioRxiv2023

Periodic and aperiodic changes to cortical EEG in response to pharmacological manipulation

Cortical electroencephalograms (EEG) may help understanding of neuropsychiatric illness and new treatment mechanisms. The aperiodic component (1/f) of EEG power spectra is often treated as noise, but recent studies suggest that changes to the aperiodic exponent of power spectra may reflect changes in excitation/inhibition (E/I) balance, a concept linked to antidepressant effects, epilepsy, autism, and other clinical conditions. One confound of previous studies is behavioral state, because factors associated with behavioral state other than E/I ratio may alter EEG parameters. Thus, to test the robustness of the aperiodic exponent as a predictor of E/I ratio, we analyzed active exploration in mice using video EEG following various pharmacological manipulations with the Fitting Oscillations & One Over F (FOOOF) algorithm. We found that GABAA receptor (GABAAR) positive allosteric modulators increased the aperiodic exponent, consistent with the hypothesis that an increased exponent signals enhanced cortical inhibition, but other drugs (ketamine and GABAAR antagonists at sub-convulsive doses) did not follow the prediction. To tilt E/I ratio more selectively toward excitation, we suppressed the activity of parvalbumin (PV) interneurons with Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). Contrary to our expectations and studies demonstrating increased cortical activity following PV suppression, circuit disinhibition with the DREADD increased the aperiodic exponent. We conclude that the aperiodic exponent of EEG power spectra does not yield a universally reliable marker of E/I ratio. Alternatively, the concept of E/I state may be sufficiently oversimplified that it cannot be mapped readily onto an EEG parameter. Significance StateBmentNeuropsychiatric illness is widely prevalent and debilitating. Causes are not well understood, but some hypotheses point toward altered excitation/inhibition (E/I) balance. Here, we use cortical electroencephalograms (EEG) in mice, given applicability of cortical EEG across species, and evaluate the impact of validated drugs, including anxiolytics (pentobarbital and diazepam), along with novel rapid-acting antidepressants (ketamine and allopregnanolone). We focus on analyzing the aperiodic component of EEG power spectra, which may be associated with changes in E/I ratio. We show that aperiodic exponent of EEG power spectra is not a reliable marker of E/I ratio. Moreover, the concept of E/I ratio may be too broad and complex to be defined by an EEG parameter.

neuroscience↗

bioRxiv2023

Chronic striatal cholinergic interneuron excitation induces clinically-relevant dystonic behavior in mice

Dystonia is common, debilitating, often medically refractory, and difficult to diagnose. The gold standard for both clinical and mouse model dystonia evaluation is subjective assessment, ideally by expert consensus. However, this subjectivity makes translational quantification of clinically-relevant dystonia metrics across species nearly impossible. Many mouse models of genetic dystonias display abnormal striatal cholinergic interneuron excitation, but few display subjectively dystonic features. Therefore, whether striatal cholinergic interneuron pathology causes dystonia remains unknown. To address these critical limitations, we first demonstrate that objectively quantifiable leg adduction variability correlates with leg dystonia severity in people. We then show that chemogenetic excitation of striatal cholinergic interneurons in mice causes comparable leg adduction variability in mice. This clinically-relevant dystonic behavior in mice does not occur with acute excitation, but rather develops after 14 days of ongoing striatal cholinergic interneuron excitation. This requirement for prolonged excitation recapitulates the clinically observed phenomena of a delay between an inciting brain injury and subsequent dystonia manifestation and demonstrates a causative link between chronic striatal cholinergic interneuron excitation and clinically-relevant dystonic behavior in mice. Therefore, these results support targeting striatal ChIs for dystonia drug development and suggests early treatment in the window following injury but prior to dystonia onset. One Sentence SummaryChronic excitation of dorsal striatal cholinergic interneuron causes clinically-relevant dystonic phenotypes in mice

neuroscience↗