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Salt-inducible kinases (SIKs), which comprise a family of three homologous serine-threonine kinases, were first described for their role in sodium sensing but have since been shown to regulate multiple aspects of physiology. These kinases are activated or deactivated in response to extracellular signals that are cell surface receptor mediated and go on to phosphorylate multiple targets including the transcription cofactors CRTC1-3 and the class IIa histone deacetylases (HDACs). Thus, the SIK family conveys signals about the cellular environment to reprogram transcriptional and posttranscriptional processes in response. In this manner, SIKs have been shown to regulate metabolic responses to feeding/fasting, cell division and oncogenesis, inflammation, immune responses, and most recently, sleep and circadian rhythms. Sleep and circadian rhythms are master regulators of physiology and are exquisitely sensitive to regulation by environmental light and physiological signals such as the need for sleep. Salt-inducible kinases have been shown to be central to the molecular regulation of both these processes. Here, we summarize the molecular mechanisms by which SIKs control these different domains of physiology and highlight where there is mechanistic overlap with sleep/circadian rhythm control.
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Proteínas Serina-Treonina Quinasas , Factores de Transcripción , Humanos , Proteínas Serina-Treonina Quinasas/metabolismo , Factores de Transcripción/metabolismo , Cloruro de Sodio , Ritmo Circadiano , SueñoRESUMEN
Retinal photoreceptors entrain the circadian system to the solar day. This photic resetting involves cAMP response element binding protein (CREB)-mediated upregulation of Per genes within individual cells of the suprachiasmatic nuclei (SCN). Our detailed understanding of this pathway is poor, and it remains unclear why entrainment to a new time zone takes several days. By analyzing the light-regulated transcriptome of the SCN, we have identified a key role for salt inducible kinase 1 (SIK1) and CREB-regulated transcription coactivator 1 (CRTC1) in clock re-setting. An entrainment stimulus causes CRTC1 to coactivate CREB, inducing the expression of Per1 and Sik1. SIK1 then inhibits further shifts of the clock by phosphorylation and deactivation of CRTC1. Knockdown of Sik1 within the SCN results in increased behavioral phase shifts and rapid re-entrainment following experimental jet lag. Thus SIK1 provides negative feedback, acting to suppress the effects of light on the clock. This pathway provides a potential target for the regulation of circadian rhythms.
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Relojes Circadianos , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Transporte Activo de Núcleo Celular , Animales , Ritmo Circadiano , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Técnicas de Silenciamiento del Gen , Ratones , Ratones Endogámicos C57BL , Proteínas Serina-Treonina Quinasas/genética , ARN Interferente Pequeño/metabolismo , Opsinas de Bastones/genética , Opsinas de Bastones/metabolismo , Núcleo Supraquiasmático/metabolismo , Factores de Transcripción/metabolismo , Transcripción GenéticaRESUMEN
Human immunodeficiency virus type 1 (HIV-1) causes a major burden on global health, and eradication of latent virus infection is one of the biggest challenges in the field. The circadian clock is an endogenous timing system that oscillates with a ~24 h period regulating multiple physiological processes and cellular functions, and we recently reported that the cell intrinsic clock regulates rhythmic HIV-1 replication. Salt inducible kinases (SIK) contribute to circadian regulatory networks, however, there is limited evidence for SIKs regulating HIV-1 infection. Here, we show that pharmacological inhibition of SIKs perturbed the cellular clock and reduced rhythmic HIV-1 replication in circadian synchronised cells. Further, SIK inhibitors or genetic silencing of Sik expression inhibited viral replication in primary cells and in a latency model, respectively. Overall, this study demonstrates a role for salt inducible kinases in regulating HIV-1 replication and latency reactivation, which can provide innovative routes to better understand and target latent HIV-1 infection.
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Infecciones por VIH , VIH-1 , Humanos , VIH-1/genética , Latencia del Virus/genética , Replicación ViralRESUMEN
Bipolar disorder is a chronic neuropsychiatric condition associated with mood instability, where patients present significant sleep and circadian rhythm abnormalities. Currently, the pathophysiology of bipolar disorder remains elusive, but treatment with lithium continues as the benchmark pharmacotherapy, functioning as a potent mood stabilizer in most, but not all patients. Lithium is well documented to induce period lengthening and amplitude enhancement of the circadian clock. Based on this, we sought to investigate whether lithium differentially impacts circadian rhythms in bipolar patient cell lines and crucially if lithium's effect on the clock is fundamental to its mood-stabilizing effects. We analyzed the circadian rhythms of bipolar patient-derived fibroblasts (n = 39) and their responses to lithium and three further chronomodulators. Here we show, relative to controls (n = 23), patients exhibited a wider distribution of circadian period (p < 0.05), and that patients with longer periods were medicated with a wider range of drugs, suggesting lower effectiveness of lithium. In agreement, patient fibroblasts with longer periods displayed muted circadian responses to lithium as well as to other chronomodulators that phenocopy lithium. These results show that lithium differentially impacts the circadian system in a patient-specific manner and its effect is dependent on the patient's circadian phenotype. We also found that lithium-induced behavioral changes in mice were phenocopied by modulation of the circadian system with drugs that target the clock, and that a dysfunctional clock ablates this response. Thus, chronomodulatory compounds offer a promising route to a novel treatment paradigm. These findings, upon larger-scale validation, could facilitate the implementation of a personalized approach for mood stabilization.
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Trastorno Bipolar , Litio , Animales , Trastorno Bipolar/tratamiento farmacológico , Ritmo Circadiano , Fibroblastos , Humanos , Compuestos de Litio/farmacología , RatonesRESUMEN
Circadian rhythms are 24-h rhythms in physiology and behaviour generated by molecular clocks, which serve to coordinate internal time with the external world. The circadian system is a master regulator of nearly all physiology and its disruption has major consequences on health. Sleep and circadian rhythm disruption (SCRD) is a ubiquitous feature in today's 24/7 society, and studies on shift-workers have shown that SCRD can lead not only to cognitive impairment, but also metabolic syndrome and psychiatric illness including depression (1,2). Mouse models of clock mutants recapitulate these deficits, implicating mechanistic and causal links between SCRD and disease pathophysiology (3-5). Importantly, treating clock disruption reverses and attenuates these adverse health states in animal models (6,7), thus establishing the circadian system as a novel therapeutic target. Significantly, circadian and clock-controlled gene mutations have recently been identified by Genome-Wide Association Studies (GWAS) in the aetiology of sleep, mental health and metabolic disorders. This review will focus upon the genetics of circadian rhythms in sleep and health.
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Ritmo Circadiano/genética , Ritmo Circadiano/fisiología , Sueño/genética , Animales , Relojes Circadianos/genética , Relojes Circadianos/fisiología , Depresión/genética , Humanos , Trastornos Mentales/genética , Trastornos Mentales/fisiopatología , Ratones , Modelos Animales , Sueño/fisiologíaRESUMEN
Inositol 1,4,5-trisphosphate (IP3 ) is a universal signalling molecule that releases calcium from stores within cells by activating the IP3 receptor. Although chemical tools that modulate the IP3 receptor exist, none is ideal due to trade offs between potency, selectivity and cell permeability, and their chemical properties make them challenging starting points for optimisation. Therefore, to find new leads, we used virtual screening to scaffold hop from IP3 by using the program ROCS to perform a 3D ligand-based screen of the ZINC database of purchasable compounds. We then used the program FRED to dock the top-ranking hits into the IP3 binding pocket of the receptor. We tested the 12 highest-scoring hits in a calcium-release bioassay and identified SI-9 as a partial agonist. SI-9 competed with [(3) H]IP3 binding, and reduced histamine-induced calcium signalling in HeLa cells. SI-9 has a novel 2D scaffold that represents a tractable lead for designing improved IP3 receptor modulators.
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Receptores de Inositol 1,4,5-Trifosfato/agonistas , Inositol 1,4,5-Trifosfato/análogos & derivados , Inositol 1,4,5-Trifosfato/farmacología , Bibliotecas de Moléculas Pequeñas/química , Bibliotecas de Moléculas Pequeñas/farmacología , Calcio/metabolismo , Diseño de Fármacos , Células HeLa , Humanos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Ligandos , Simulación del Acoplamiento MolecularRESUMEN
Platelets play a vital role in maintaining haemostasis. Human platelet activation depends on Ca2+ release, leading to cell activation, granule secretion and aggregation. NAADP (nicotinic acid-adenine dinucleotide phosphate) is a Ca2+-releasing second messenger that acts on acidic Ca2+ stores and is used by a number of mammalian systems. In human platelets, NAADP has been shown to release Ca2+ in permeabilized human platelets and contribute to thrombin-mediated platelet activation. In the present study, we have further characterized NAADP-mediated Ca2+ release in human platelets in response to both thrombin and the GPVI (glycoprotein VI)-specific agonist CRP (collagen-related peptide). Using a radioligand-binding assay, we reveal an NAADP-binding site in human platelets, indicative of a platelet NAADP receptor. We also found that NAADP releases loaded 45Ca2+ from intracellular stores and that total platelet Ca2+ release is inhibited by the proton ionophore nigericin. Ned-19, a novel cell-permeant NAADP receptor antagonist, competes for the NAADP-binding site in platelets and can inhibit both thrombin- and CRP-induced Ca2+ release in human platelets. Ned-19 has an inhibitory effect on platelet aggregation, secretion and spreading. In addition, Ned-19 extends the clotting time in whole-blood samples. We conclude that NAADP plays an important role in human platelet function. Furthermore, the development of Ned-19 as an NAADP receptor antagonist provides a potential avenue for platelet-targeted therapy and the regulation of thrombosis.
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Plaquetas/metabolismo , NADP/análogos & derivados , Activación Plaquetaria/fisiología , Plaquetas/efectos de los fármacos , Calcio/metabolismo , Señalización del Calcio/fisiología , Carbolinas/farmacología , Proteínas Portadoras/metabolismo , Humanos , NADP/metabolismo , Péptidos/metabolismo , Piperazinas/farmacología , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Trombina/farmacologíaRESUMEN
Sleep and circadian rhythm disruption (SCRD), as encountered during shift work, increases the risk of respiratory viral infection including SARS-CoV-2. However, the mechanism(s) underpinning higher rates of respiratory viral infection following SCRD remain poorly characterized. To address this, we investigated the effects of acute sleep deprivation on the mouse lung transcriptome. Here we show that sleep deprivation profoundly alters the transcriptional landscape of the lung, causing the suppression of both innate and adaptive immune systems, disrupting the circadian clock, and activating genes implicated in SARS-CoV-2 replication, thereby generating a lung environment that could promote viral infection and associated disease pathogenesis. Our study provides a mechanistic explanation of how SCRD increases the risk of respiratory viral infections including SARS-CoV-2 and highlights possible therapeutic avenues for the prevention and treatment of respiratory viral infection.
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Human immunodeficiency virus 1 (HIV-1) causes major health burdens worldwide and still lacks curative therapies and vaccines. Circadian rhythms are endogenous daily oscillations that coordinate an organism's response to its environment and invading pathogens. Peripheral viral loads of HIV-1 infected patients show diurnal variation; however, the underlying mechanisms remain unknown. Here, we demonstrate a role for the cell-intrinsic clock to regulate rhythmic HIV-1 replication in circadian-synchronized systems. Silencing the circadian activator Bmal1 abolishes this phenotype, and we observe BMAL1 binding to the HIV-1 promoter. Importantly, we show differential binding of the nuclear receptors REV-ERB and ROR to the HIV-long terminal repeat at different circadian times, demonstrating a dynamic interplay in time-of-day regulation of HIV-1 transcription. Bioinformatic analysis shows circadian regulation of host factors that control HIV-1 replication, providing an additional mechanism for rhythmic viral replication. This study increases our understanding of the circadian regulation of HIV-1, which can ultimately inform new therapies.
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Cyclic ADP-ribose (cADPR) is a second messenger that acts on ryanodine receptors to mobilize Ca(2+). cADPR has a net negative charge at physiological pH making it not passively membrane permeant thereby requiring it to be injected, electroporated or loaded via liposomes. Such membrane impermeance of other charged intracellular messengers (including cyclic AMP, inositol 1,4,5-trisphosphate and nicotinic acid adenine dinucleotide phosphate) and fluorescent dyes (including fura-2 and fluorescein) has been overcome by synthesizing masked analogs (prodrugs), which are passively permeant and hydrolyzed to the parent compound inside cells. We now report the synthesis and biological activity of acetoxymethyl (AM) and butoxymethyl (BM) analogs of cADPR. Extracellular addition of cADPR-AM or cADPR-BM to neuronal cells in primary culture or PC12 neuroblastoma cells induced increases in cytosolic Ca(2+). Pre-incubation of PC12 cells with thapsigargin, ryanodine or caffeine eliminated the response to cADPR-AM, whereas the response still occurred in the absence of extracellular Ca(2+). Combined, these data demonstrate that masked cADPR analogs are cell-permeant and biologically active. We hope these cell-permeant tools will facilitate cADPR research and reveal its diverse physiological functions.
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Permeabilidad de la Membrana Celular , ADP-Ribosa Cíclica/análogos & derivados , ADP-Ribosa Cíclica/metabolismo , Animales , Transporte Biológico , Cafeína/farmacología , Calcio/metabolismo , Permeabilidad de la Membrana Celular/efectos de los fármacos , ADP-Ribosa Cíclica/síntesis química , Células PC12 , Ratas , Rianodina/farmacología , Erizos de Mar , Tapsigargina/farmacologíaAsunto(s)
Analgésicos Opioides/uso terapéutico , Dolor Crónico/tratamiento farmacológico , Traumatismos Ocupacionales/tratamiento farmacológico , Trastornos Relacionados con Opioides/epidemiología , Indemnización para Trabajadores/legislación & jurisprudencia , Dolor Crónico/psicología , Prescripciones de Medicamentos , Humanos , Internet , Guías de Práctica Clínica como Asunto , Pautas de la Práctica en Medicina , Indemnización para Trabajadores/estadística & datos numéricosRESUMEN
Circadian entrainment in mice relies primarily on photic cues that trigger the transcription of the core clock genes Period1/2 in the suprachiasmatic nucleus (SCN), thus aligning the phase of the clock with the dawn/dusk cycle. It has been shown previously that this pathway is directly regulated by adenosine signalling and that adenosine A2A/A1 receptor antagonists can both enhance photic entrainment and phase shift circadian rhythms of wheel-running behaviour in mice. In this study, we tested the ability of CT1500, a clinically safe adenosine A2A/A1 receptor antagonist to effect circadian entrainment. We show that CT1500 lengthens circadian period in SCN ex vivo preparations. Furthermore, we show in vivo that a single dose of CT1500 enhances re-entrainment to a shifted light dark cycle in a dose-dependent manner in mice and also phase shifts the circadian clock under constant dark with a clear time-of-day related pattern. The phase response curve shows CT1500 causes phase advances during the day and phase delays at dusk. Finally, we show that daily timed administration of CT1500 can entrain the circadian clock to a 24 h rhythm in free-running mice. Collectively, these data support the use of CT1500 in the treatment of disorders of circadian entrainment.
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Before a sperm can fertilize an egg it must undergo a final activation step induced by the egg termed the acrosome reaction. During the acrosome reaction a lysosome-related organelle, the acrosome, fuses with the plasma membrane to release hydrolytic enzymes and expose an egg-binding protein. Because NAADP (nicotinic acid adenine dinucleotide phosphate) releases Ca(2+) from acidic lysosome-related organelles in other cell types, we investigated a possible role for NAADP in mediating the acrosome reaction. We report that NAADP binds with high affinity to permeabilized sea urchin sperm. Moreover, we used Mn(2+) quenching of luminal fura-2 and (45)Ca(2+) to directly demonstrate NAADP regulation of a cation channel on the acrosome. Additionally, we show that NAADP synthesis occurs through base exchange and is driven by an increase in Ca(2+). We propose a new model for acrosome reaction signaling in which Ca(2+) influx initiated by egg jelly stimulates NAADP synthesis and that this NAADP acts on its receptor/channel on the acrosome to release Ca(2+) to drive acrosomal exocytosis.
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Reacción Acrosómica , NADP/análogos & derivados , Espermatozoides/metabolismo , Acrosoma/metabolismo , Animales , Calcio/química , Cationes , Exocitosis , Femenino , Fura-2/química , Masculino , Manganeso/química , NADP/química , Unión Proteica , Erizos de Mar , Transducción de SeñalRESUMEN
Research into the biological role of the Ca(2+)-releasing second messenger NAADP (nicotinic acid adenine dinucleotide phosphate) has been hampered by a lack of chemical probes. To find new chemical probes for exploring NAADP signaling, we turned to virtual screening, which can evaluate millions of molecules rapidly and inexpensively. We used NAADP as the query ligand to screen the chemical library ZINC for compounds with similar three-dimensional shape and electrostatic properties. We tested the top-ranking hits in a sea urchin egg bioassay and found that one hit, Ned-19, blocks NAADP signaling at nanomolar concentrations. In intact cells, Ned-19 blocked NAADP signaling and fluorescently labeled NAADP receptors. Moreover, we show the utility of Ned-19 as a chemical probe by using it to demonstrate that NAADP is a key causal link between glucose sensing and Ca(2+) increases in mouse pancreatic beta cells.
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NADP/análogos & derivados , Animales , Carbolinas/química , Carbolinas/farmacología , ADP-Ribosa Cíclica/farmacología , Inositol 1,4,5-Trifosfato/farmacología , Células Secretoras de Insulina/efectos de los fármacos , Ratones , Modelos Moleculares , Estructura Molecular , NADP/química , NADP/metabolismo , Óvulo/química , Piperazinas/química , Piperazinas/farmacología , Erizos de Mar , Bibliotecas de Moléculas PequeñasRESUMEN
The accumulation of adenosine is strongly correlated with the need for sleep and the detection of sleep pressure is antagonised by caffeine. Caffeine also affects the circadian timing system directly and independently of sleep physiology, but how caffeine mediates these effects upon the circadian clock is unclear. Here we identify an adenosine-based regulatory mechanism that allows sleep and circadian processes to interact for the optimisation of sleep/wake timing in mice. Adenosine encodes sleep history and this signal modulates circadian entrainment by light. Pharmacological and genetic approaches demonstrate that adenosine acts upon the circadian clockwork via adenosine A1/A2A receptor signalling through the activation of the Ca2+ -ERK-AP-1 and CREB/CRTC1-CRE pathways to regulate the clock genes Per1 and Per2. We show that these signalling pathways converge upon and inhibit the same pathways activated by light. Thus, circadian entrainment by light is systematically modulated on a daily basis by sleep history. These findings contribute to our understanding of how adenosine integrates signalling from both light and sleep to regulate circadian timing in mice.
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Adenosina/metabolismo , Trastornos Cronobiológicos/fisiopatología , Relojes Circadianos/efectos de los fármacos , Sueño/fisiología , Animales , Encéfalo/patología , Cafeína/farmacología , Línea Celular Tumoral , Trastornos Cronobiológicos/tratamiento farmacológico , Trastornos Cronobiológicos/etiología , Trastornos Cronobiológicos/patología , Relojes Circadianos/fisiología , Ritmo Circadiano/efectos de los fármacos , Ritmo Circadiano/fisiología , Modelos Animales de Enfermedad , Humanos , Luz , Masculino , Ratones , Ratones Transgénicos , Proteínas Circadianas Period/genética , Proteínas Circadianas Period/metabolismo , Fotoperiodo , Quinazolinas/administración & dosificación , Receptor de Adenosina A1/metabolismo , Receptor de Adenosina A2A/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Transducción de Señal/efectos de la radiación , Sueño/efectos de los fármacos , Privación de Sueño/complicaciones , Triazoles/administración & dosificaciónRESUMEN
We have optimised a reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of SARS-CoV-2 from extracted RNA for clinical application. We improved the stability and reliability of the RT-LAMP assay by the addition of a temperature-dependent switch oligonucleotide to reduce self- or off-target amplification. We then developed freeze-dried master mix for single step RT-LAMP reaction, simplifying the operation for end users and improving long-term storage and transportation. The assay can detect as low as 13 copies of SARS-CoV2 RNA per reaction (25-µL). Cross reactivity with other human coronaviruses was not observed. We have applied the new RT-LAMP assay for testing clinical extracted RNA samples extracted from swabs of 72 patients in the UK and 126 samples from Greece and demonstrated the overall sensitivity of 90.2% (95% CI 83.8-94.7%) and specificity of 92.4% (95% CI 83.2-97.5%). Among 115 positive samples which Ct values were less than 34, the RT-LAMP assay was able to detect 110 of them with 95.6% sensitivity. The specificity was 100% when RNA elution used RNase-free water. The outcome of RT-LAMP can be reported by both colorimetric detection and quantifiable fluorescent reading. Objective measures with a digitized reading data flow would allow for the sharing of results for local or national surveillance.
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Prueba de Ácido Nucleico para COVID-19/métodos , Técnicas de Diagnóstico Molecular/métodos , Técnicas de Amplificación de Ácido Nucleico/métodos , Prueba de Ácido Nucleico para COVID-19/normas , Humanos , Técnicas de Diagnóstico Molecular/normas , Técnicas de Amplificación de Ácido Nucleico/normas , Sensibilidad y EspecificidadRESUMEN
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca(2+)-releasing messenger. Biological data suggest that its receptor has two binding sites: one high-affinity locking site and one low-affinity opening site. To directly address the presence and function of these putative binding sites, we synthesized and tested analogues of the NAADP antagonist Ned-19. Ned-19 itself inhibits both NAADP-mediated Ca(2+) release and NAADP binding. A fluorometry bioassay was used to assess NAADP-mediated Ca(2+) release, whereas a radioreceptor assay was used to assess binding to the NAADP receptor (only at the high-affinity site). In Ned-20, the fluorine is para rather than ortho as in Ned-19. Ned-20 does not inhibit NAADP-mediated Ca(2+) release but inhibits NAADP binding. Conversely, Ned-19.4 (a methyl ester of Ned-19) inhibits NAADP-mediated Ca(2+) release but cannot inhibit NAADP binding. Furthermore, Ned-20 prevents the self-desensitization response characteristic of NAADP in sea urchin eggs, confirming that this response is mediated by a high-affinity allosteric site to which NAADP binds in the radioreceptor assay. Collectively, these data provide the first direct evidence for two binding sites (one high- and one low-affinity) on the NAADP receptor.
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Carbolinas/metabolismo , NADP/análogos & derivados , Piperazinas/metabolismo , Receptores de Superficie Celular/metabolismo , Animales , Sitios de Unión , Bioensayo/métodos , Calcio/metabolismo , Carbolinas/química , Estructura Molecular , NADP/antagonistas & inhibidores , Oocitos/citología , Oocitos/metabolismo , Piperazinas/química , Ensayo de Unión Radioligante , Receptores de Superficie Celular/genética , Erizos de MarRESUMEN
The suprachiasmatic nucleus (SCN) is a complex structure dependent upon multiple mechanisms to ensure rhythmic electrical activity that varies between day and night, to determine circadian adaptation and behaviours. SCN neurons are exposed to glutamate from multiple sources including from the retino-hypothalamic tract and from astrocytes. However, the mechanism preventing inappropriate post-synaptic glutamatergic effects is unexplored and unknown. Unexpectedly we discovered that TRESK, a calcium regulated two-pore potassium channel, plays a crucial role in this system. We propose that glutamate activates TRESK through NMDA and AMPA mediated calcium influx and calcineurin activation to then oppose further membrane depolarisation and rising intracellular calcium. Hence, in the absence of TRESK, glutamatergic activity is unregulated leading to membrane depolarisation, increased nocturnal SCN firing, inverted basal calcium levels and impaired sensitivity in light induced phase delays. Our data reveals TRESK plays an essential part in SCN regulatory mechanisms and light induced adaptive behaviours.
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Adaptación Ocular , Oscuridad , Canales de Potasio/metabolismo , Núcleo Supraquiasmático/fisiología , Animales , Conducta Animal , Calcio/metabolismo , Ácido Glutámico/metabolismo , Luz , Potenciales de la Membrana/efectos de la radiación , Ratones Endogámicos C57BL , Canales de Potasio/deficiencia , Transducción de Señal/efectos de la radiación , Núcleo Supraquiasmático/efectos de la radiaciónRESUMEN
Lithium, commonly used to treat bipolar disorder, potentiates the ability of the muscarinic agonist pilocarpine to induce seizures in rodents. As this potentiation by lithium is reversed by the administration of myo-inositol, the potentiation may be mediated by inhibition of inositol monophosphatase (IMPase), a known target of lithium. Recently, we demonstrated that ebselen is a 'lithium mimetic' in regard to behaviours in both mice and man. Ebselen inhibits IMPase in vitro and lowers myo-inositol in vivo in the brains of mice and men, making ebselen the only known inhibitor of IMPase, other than lithium, that penetrates the blood-brain barrier. Our objective was to determine the effects of ebselen on sensitization to pilocarpine-induced seizures and neural activity. We administered ebselen at different doses and time intervals to mice, followed by injection of a sub-seizure dose of pilocarpine. We assessed seizure and neural activity by a subjective seizure rating scale, by monitoring tremors, and by induction of the immediate early gene c-fos. In contrast to lithium, ebselen did not potentiate the ability of pilocarpine to induce seizures. Unexpectedly, ebselen inhibited pilocarpine-induced tremor as well as pilocarpine-induced increases in c-fos mRNA levels. Both lithium and ebselen inhibit a common target, IMPase, but only lithium potentiates pilocarpine-induced seizures, consistent with their polypharmacology at diverse molecular targets. We conclude that ebselen does not potentiate pilocarpine-induced seizures and instead, reduces pilocarpine-mediated neural activation. This lack of potentiation of muscarinic sensitization may be one reason for the lack of side-effects observed with ebselen treatment clinically.