Search

Abigail I Nash,1 Ibrahim Turkoz,2 Adam J Savitz,2 Maju Mathews,2 Edward Kim1 1Janssen Scientific Affairs, LLC, Titusville, NJ 08560, USA; 2Janssen Research and Development, LLC, Titusville, NJ 08560, USA Purpose: Long-acting injectable (LAI) antipsychotic paliperidone palmitate 3-month formulation (PP3M) is indicated in the United States for the treatment of schizophrenia only after adequate treatment with paliperidone palmitate 1-month formulation (PP1M) for ≥4 months. This analysis aimed to identify patient and disease characteristics during PP1M treatment associated with greater likelihood of achieving remission after transition to PP3M.Methods: A post hoc analysis of a randomized, Phase III, double-blind, noninferiority trial of PP3M vs PP1M (ClinicalTrials.gov identifier: NCT01515423) was conducted in adult patients with schizophrenia. Patients achieving clinical stability after 17 weeks of open-label PP1M were randomized to 48 weeks of double-blind treatment with PP3M or PP1M. The primary objective of this exploratory post hoc analysis was to identify demographic and/or clinical variables associated with persistent remission after treatment with PP3M. Multiple logistic regression analysis identified the following significant predictors of remission: Positive and Negative Syndrome Scale (PANSS) Marder negative symptom factor score, Clinical Global Impression-Severity (CGI-S) total score, and Personal and Social Performance (PSP) total score.Results: At double-blind baseline, a 1-point reduction in Marder negative symptom factor score was associated with a 20% increase in the odds of achieving remission after PP3M treatment; 1-point reduction in CGI-S was associated with a doubling in remission odds; and 7- and 10-point improvements in PSP scores, respectively, were associated with 42% and 65% increases in remission odds.Conclusion: Patients with early clinically meaningful improvements in disease symptoms and severity while establishing stable PP1M dosage are more likely to achieve remission after transition to PP3M. Keywords: long-acting injectable, symptomatic remission, double-blind treatment

Background: Esketamine (ESK) nasal spray, taken with oral antidepressant therapy, is approved for the treatment of depressive symptoms in adults with major depressive disorder (MDD) with acute suicidal ideation or behavior. In pooled analyses of two pivotal phase 3 studies, ASPIRE I and II, remission rates were consistently higher among patients with MDD with active suicidality who were treated with ESK + standard of care (SOC) versus placebo (PBO) + SOC at all time points in the double-blind and most time points in the follow-up phases. The current analysis of the ASPIRE data sets assessed the effect of ESK + SOC versus PBO + SOC on additional remission-related endpoints: time to achieving remission and consistent remission, proportion of patients in remission and consistent remission, and days in remission., Methods: Post hoc analysis of pooled data from ASPIRE I and II (N = 451). Remission and consistent remission were defined as Montgomery-Åsberg Depression Rating Scale (MADRS) total score ≤ 12 at any given visit or two consecutive visits, respectively. Combined endpoints utilizing Clinical Global Impression-Severity of Suicidality-revised version [CGI-SS-r] ≤ 1 (i.e., not suicidal/questionably suicidal) along with the remission and consistent remission definitions (i.e., MADRS total score ≤ 12) were also examined., Results: The median times to remission and consistent remission of MDD were significantly shorter in ESK + SOC versus PBO + SOC (15 versus 23 [p = 0.005] and 23 versus 50 days [p = 0.007], respectively) and a greater proportion of patients in ESK + SOC achieved remission and consistent remission by Day 25 (65.2% versus 55.5% and 54.2% versus 39.8%, respectively). Similar results were obtained using the combined endpoint for both remission definitions. The median percent of days in remission during the double-blind treatment phase was significantly greater in ESK + SOC (27.1% or 5 days) versus PBO + SOC (8.3% or 2 days; p = 0.006), and the significant difference was maintained during follow-up., Conclusion: Treatment with ESK + SOC versus PBO + SOC resulted in significantly shorter time to remission, greater proportion of patients in remission, and greater percent of days in remission using increasingly rigorous definitions of remission. These findings underscore the clinical benefits of ESK for adults with MDD with suicidality., Trial Registration: ClinicalTrials.gov registry NCT03039192 (registered February 1, 2017) and NCT03097133 (registered March 31, 2017)., (© 2023. BioMed Central Ltd., part of Springer Nature.)

GABA A receptor-positive modulators are well-known to induce sedation, sleep, and general anesthesia. Conversely, GABA A receptor negative allosteric modulators (GABA A RNAMs) can increase arousal and induce seizures. Motivated by our studies with patients with hypersomnia, and our discovery that two GABA A RNAMs can restore the Excitation/Inhibition (E/I) balance in vitro and arousal in vivo, we chose to screen 11 compounds that have been reported to modulate arousal, to see if they shared a GABA-related mechanism. We determined modulation with both conventional and microfluidic patch clamp methods. We found that receptor activation was variably modulated by all 11 compounds: Rifampicin (RIF), Metronidazole (MET), Minocycline (MIN), Erythromycin (ERY), Ofloxacin (OFX), Chloroquine (CQ), Hydroxychloroquine sulfate (HCQ), Flumazenil (FLZ), Pentylenetetrazol (PTZ), (-)-Epigallocatechin Gallate (EGCG), and clarithromycin (CLR). The computational modeling of modulator-receptor interactions predicted drug action at canonical binding sites and novel orphan sites on the receptor. Our findings suggest that multiple avenues of investigation are now open to investigate large and brain-penetrant molecules for the treatment of patients with diminished CNS E/I balance.

Purpose: This study aimed to characterize patients with treatment-resistant depression (TRD) initiating esketamine or conventional therapies., Methods: Adults with major depressive disorder (MDD) were selected from the IBM MarketScan Databases. A claims-based algorithm identified patients with evidence of TRD, defined as initiation of a new antidepressant therapy after 2 different antidepressant trials of adequate dose and duration during the most recent major depressive episode. Patients receiving treatment on/after March 5, 2019 (esketamine approval date for TRD), were classified to the esketamine cohort if they newly initiated esketamine (index date) or to the TRD conventional therapies cohorts if they newly initiated electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), or pharmacologic therapies (index date was the therapy initiation date, prioritizing ECT, then TMS, then pharmacologic antidepressant therapies). Patient characteristics in the 6 months before therapy initiation were described., Findings: The esketamine cohort included 246 patients (mean age, 46.5 years; 63.0% female), and the TRD conventional therapies cohorts included 104,164 patients (mean age, 46.9 years; 74.8% female; 0.4% initiated ECT, 1.2% initiated TMS). During the 6 months preindex, in the esketamine and TRD conventional therapies cohorts, 77.6% and 41.4% received psychotherapy and 82.9% and 34.2% had a psychiatrist visit, respectively. Most patients had outpatient care for MDD in the esketamine (91.9%) and TRD conventional therapies (63.6%) cohorts; 57.3% and 21.0% received care at specialized mental health care settings. MDD was classified as "severe" among 81.3% and 35.1% of patients in the esketamine and TRD conventional therapies cohorts . Preindex mental health-related (MHR) inpatient admissions and emergency department visits were identified in 12.2% and 16.3% of the esketamine cohort and in 8.2% and 10.3% of the TRD conventional therapies cohort. Before therapy initiation, 34.6% and 17.6% of the esketamine and TRD conventional therapies cohorts received ≥3 unique antidepressants. Suicidal ideation or behavior was observed in 8.5% and 3.6% of the esketamine and TRD conventional therapies cohorts pretherapy initiation. Mean monthly all-cause health care costs in the esketamine cohort were $2532 (58.2% MHR); in the TRD conventional therapies cohorts, costs were $1873 (32.4% MHR)., Implications: Among patients with TRD, those initiating esketamine relative to conventional therapies displayed higher MDD severity, used more MHR inpatient/emergency department services and antidepressant treatments, and incurred higher health care costs 6 months pretherapy initiation. These findings suggest potential benefits of identifying and treating patients with TRD earlier with more effective treatments and should inform payers in consideration of esketamine coverage., Competing Interests: Declaration of Interest Ms Zhdanava, Mr Pilon, Ms Morrison, Ms Shah, and Mr Lefebvre are employees of Analysis Group, Inc., a consulting company that has provided paid consulting services to Janssen Scientific Affairs, LLC, which funded the development and conduct of this study and manuscript. Ms Karkare and Ms Joshi are employees of Janssen Scientific Affairs, LLC, and stockholders of Johnson & Johnson. Dr Nash was an employee of Janssen Scientific Affairs, LLC, at the time of study conduct. The sponsor was involved in the study design, data collection, data analysis, manuscript preparation, and publication decisions., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: This study examined MDD treatment regimens received during the first observed and treated major depressive episode (MDE) among US veterans., Methods: This retrospective study, conducted using the Veterans Health Administration (VHA) database, supplemented with Medicare Part A/B/D data, included adults with ≥1 MDD diagnosis (index date) between 10/1/2015-2/28/2017 and ≥1 line of therapy (LOT) within the first observed complete MDE. Patient baseline (6-month pre-index) characteristics and up to six LOTs received during the first observed and treated MDE were assessed., Results: Of 40,240 veterans with MDD identified (mean age: 50.9 years, 83.9% male, 63.4% White, 88.6% non-Hispanic), hypertension (27.5%), hyperlipidemia (20.8%), and post-traumatic stress disorder (17.5%) were the most common baseline comorbidities. During the first observed and treated MDE, patients received a mean of 1.6 ± 1.0 LOTs, with 14.6% of patients receiving ≥3 LOTs. SSRI-monotherapy was the most commonly observed regimen in the first six LOTs, followed by SNRI-monotherapy in LOT 1 and antidepressants augmented by anticonvulsants in the remaining five LOTs. The antidepressant class of the previous LOT was commonly used in the subsequent LOT. SSRI-SSRI-SSRI was the most common LOT1-to-LOT3 sequencing pattern among patients receiving ≥3 LOTs., Limitations: The study findings are limited to data in the VHA database and may not be generalizable to the non-veteran US population., Conclusions: During the first observed and treated MDE, SSRI-monotherapy was the most common therapy in the first six LOTs. Cycling within SSRI class was the leading sequencing pattern of the first three LOTs among veterans who received ≥3 LOTs., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Abstract: To ascertain the relative importance of attributes considered when deciding to discharge patients hospitalized with major depressive disorder (MDD) and active suicidal ideation with intent, a choice-based conjoint analysis was conducted via online survey among US-based psychiatrists actively managing such patients. Potential attributes and attribute levels were identified. Attribute importance in decision to discharge and the discharge time frame were assessed. One hundred psychiatrists completed the survey. The relative importance of attributes were current MDD severity (relative importance weight [out of 100] 24.8 [95% confidence interval, 23.3-26.3]), clinician assessment of current suicidal ideation (20.8 [18.5-23.0]), previous history of suicide attempts (16.7 [15.9-17.6]), psychosocial support at discharge (13.0 [11.7-14.4]), postdischarge outpatient follow-up (9.8 [8.8-10.8]), current length of hospital stay (9.2 [8.1-10.3]), and suicidal ideation at admission (5.7 [4.8-6.6]). Thus, current clinical symptoms were considered the most important attributes by psychiatrists when discharging patients initially hospitalized with MDD and active suicidal ideation with intent., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose/background: Numerous health authority approvals of esketamine nasal spray, combined with oral antidepressant, to treat depressive symptoms in adults with major depressive disorder and acute suicidal ideation or behavior were based on 2 identically designed, double-blind, phase 3 studies., Methods/procedures: Across both ASPIRE studies (NCT03039192, NCT03097133), patients (N = 456) were randomized to esketamine 84 mg or placebo nasal spray twice weekly for 4 weeks plus comprehensive standard of care, including hospitalization and newly initiated or optimized antidepressant(s). In post hoc analyses of pooled data, changes from baseline at 24 hours after the first dose in Montgomery-Åsberg Depression Rating Scale total score and Clinical Global Impression-Severity of Suicidality-Revised, in the full cohort and in subgroups, were analyzed using analysis of covariance., Findings/results: Esketamine plus standard of care demonstrated significantly greater improvement in Montgomery-Åsberg Depression Rating Scale total score versus placebo plus standard of care at 24 hours (least square mean difference [95% confidence interval], -3.8 [-5.75 to -1.89]) and at earlier (4 hours: -3.4 [-5.05 to -1.71]) and later time points (day 25: -3.4 [-5.36 to -1.36]). The between-group difference (95% confidence interval) for change in Clinical Global Impression-Severity of Suicidality-Revised at 24 hours was -0.20 (-0.43 to 0.04) for all patients and -0.31 (-0.61 to -0.01) for those with a history of suicide attempt. Common adverse events (≥20%) during esketamine treatment were dizziness, dissociation, nausea, somnolence, and headache., Implications/conclusions: Esketamine plus comprehensive standard of care rapidly reduces depressive symptoms in patients with major depressive disorder who have acute suicidal ideation or behavior, especially in those with a history of suicide attempt, providing a new treatment option for this particularly ill and vulnerable population., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: To evaluate response to esketamine nasal spray plus an oral antidepressant (ESK + AD) at day 28 in patients with major depressive disorder ( DSM-5 ) and treatment-resistant depression (TRD) who did not meet response criteria within the first week of treatment., Methods: The current study is a pooled post hoc analysis of two phase 3, double-blind, active-controlled studies, conducted between August 2015 and February 2018, comparing ESK + AD with an oral antidepressant plus placebo (AD + PBO). Early treatment response was defined as a ≥ 50% decrease in Montgomery-Åsberg Depression Rating Scale total score at day 2 or days 2 and 8. Response rates at day 28 were determined among those not meeting early response criteria., Results: 518 patients in the analysis had day 28 observations (ESK + AD, n = 310; AD + PBO, n = 208). A greater percentage of patients treated with ESK + AD versus AD + PBO met response criteria beginning at day 2 (17.3% [55/318] vs 9.4% [19/203]) and at all subsequent timepoints, including day 28 (58.7% [182/310] vs 45.2% [94/208]). In day 2 nonresponders, 54.9% vs 44.3% (ESK + AD vs AD + PBO, respectively) achieved response at day 28 ( P  < .01). Similarly, among day 2 and 8 nonresponders, 52.1% vs 42.4% achieved response by day 28 ( P  = .01). In nonresponders at day 2 and at days 2 and 8, the odds ratio for a response at day 28 was 1.61 (95% CI, 1.09-2.40) with ESK + AD versus 1.56 (95% CI, 1.04-2.35) with AD + PBO., Conclusions: Patients with TRD without a demonstrated response within the first week of treatment may still derive benefit from a full 4-week induction course of esketamine nasal spray., Trial Registration: ClinicalTrials.gov identifiers NCT02417064 and NCT02418585., (© Copyright 2021 Physicians Postgraduate Press, Inc.)

Background and Objective: Suicidal ideation or behavior are core symptoms of major depressive disorder (MDD). This study aimed to understand heterogeneity among patients with MDD and acute suicidal ideation or behavior., Methods: Adults with a diagnosis of MDD on the same day or 6 months before a claim for suicidal ideation or behavior (index date) were identified in the MarketScan ® Databases (10/01/2014-04/30/2019). A mathematical algorithm was used to cluster patients on characteristics of care measured pre-index. Patient care pathways were described by cluster during the 12-month pre-index period and up to 12 months post-index., Results: Among 38,876 patients with MDD and acute suicidal ideation or behavior, three clusters were identified. Across clusters, pre-index exposure to mental healthcare was revealed as a key differentiator: Cluster 1 (N = 16,025) was least exposed, Cluster 2 (N = 5640) moderately exposed, and Cluster 3 (N = 17,211) most exposed. Patients whose MDD diagnosis was first observed during their index event comprised 86.0% and 72.8% of Clusters 1 and 2, respectively; in Cluster 3, all patients had an MDD diagnosis pre-index. Within 30 days post-index, in Clusters 1, 2, and 3, respectively, 79.3%, 85.2%, and 88.2% used mental health services, including outpatient visits for MDD. Within 12 months post-index, 61.5%, 91.5%, and 84.6% had one or more antidepressant claim, respectively. Per-patient index event costs averaged $5614, $6645, and $5853, respectively., Conclusions: Patients with MDD and acute suicidal ideation or behavior least exposed to the healthcare system pre-index similarly received the least care post-index. An opportunity exists to optimize treatment and follow-up with mental health services.

Background: The current analysis utilized data collected via an online patient community platform, PatientsLikeMe (PLM) to compare patient-reported experiences in patients with major depressive disorder (MDD) with suicidal ideation (MDSI) to those with MDD but without suicidal ideation., Methods: PLM members who joined PLM between May-2007 and February-2018 and reported a diagnosis of MDD were included. The MDSI cohort included patients with MDD who reported at least one suicide-related symptom at a severity greater than "none". Demographics, comorbidities, symptoms, and side-effects were compared between MDSI and MDD cohorts. Factors correlated with suicidal ideation (SI) were determined by a random forest procedure., Results: Patients in the MDSI cohort (n = 266) were younger (median age, 36 vs 44 years) with an earlier disease onset (before 30 years, 83% vs 71%), and a longer diagnosis latency (median, 4 vs 2 years) vs patients in the MDD cohort (n = 11,963). Majority of patients were women in both cohorts (73% vs 83%). Median number of psychiatric comorbidities was higher in the MDSI cohort (4 vs 3). Unprompted symptoms (e.g., loneliness, feeling of hopelessness, social anxiety, impulsivity, and self-hating thoughts) were more frequent in the MDSI cohort. Hopelessness, loneliness, anhedonia, social anxiety, and younger age were highly correlated with suicidal ideation., Conclusions: This analysis utilized patient-reported data to better understand symptoms, experiences, and characteristics of patients with MDSI compared to patients with MDD. The results identified various risk factors correlated with suicidal ideation that may help guide clinical judgement for patients with MDD who may not voluntarily report suicidal ideation.

In the setting of rising rates of obesity and metabolic syndrome, characterized in part by hyperinsulinemia, it is increasingly important to understand the mechanisms that contribute to insulin dysregulation. The higher risk for metabolic syndrome imparted by antipsychotic medication use highlights one such mechanism. Though there is great variation in the number and types of signaling pathways targeted by these medications, the one common mechanism of action is through dopamine. Dopamine's effects on insulin signaling begin at the level of insulin secretion from the pancreas and continue through the central nervous system. In a reciprocal fashion, insulin also affects dopamine signaling, with specific effects on dopamine reuptake from the synapse. This review probes the dopamine-insulin connection to provide a comprehensive examination of how antipsychotics may contribute towards insulin resistance., (Published by Elsevier B.V.)

In recent years, we have used the photocyclizations of diarylethylenes to synthesize a number of [n]phenacenes in the hope that they might be useful as the bridging groups for electron transfer processes in donor-bridge-acceptor molecules. Because [n]phenacenes with n > 5 are very insoluble, their synthesis and characterization has required the attachment of solubilizing substituents such as tert-butyl. The studies of Pascal and co-workers of some large polynuclear aromatic compounds having multiple phenyl substituents prompted us to explore the use of phenyls as alternative solubilizing groups for [n]phenacenes. Although phenyl groups turned out to provide significantly less solubilization than tert-butyl groups in these compounds, we found some interesting structural comparisons of the phenyl-substituted and tert-butyl-substituted [n]phenacenes.

Light, oxygen, voltage (LOV) domains utilize a conserved blue light-dependent mechanism to control a diverse array of effector domains in biological and engineered proteins. Variations in the kinetics and efficiency of LOV photochemistry fine-tune various aspects of the photic response. Characterization of the kinetics of a key aspect of this photochemical mechanism in EL222, a blue light responsive DNA binding protein from Erythrobacter litoralis HTCC2594, reveals unique non-Arrhenius behavior in the rate of dark-state cleavage of the photochemically generated adduct. Sequence analysis and mutagenesis studies establish that this effect stems from a Gln to Ala mutation unique to EL222 and homologous proteins from marine bacteria. Kinetic and spectroscopic analyses reveal that hydrogen bonding interactions between the FMN N1, O2, and ribityl hydroxyls and the surrounding protein regulate photocycle kinetics and stabilize the LOV active site from temperature-induced alteration in local structure. Substitution of residues interacting with the N1-O2 locus modulates adduct stability, structural flexibility, and sequestration of the active site from bulk solvent without perturbation of light-activated DNA binding. Together, these variants link non-Arrhenius behavior to specific alteration of an H-bonding network, while affording tunability of photocycle kinetics., (© 2011 American Chemical Society)

Light-oxygen-voltage (LOV) domains are blue light-activated signaling modules integral to a wide range of photosensory proteins. Upon illumination, LOV domains form internal protein-flavin adducts that generate conformational changes which control effector function. Here we advance our understanding of LOV regulation with structural, biophysical, and biochemical studies of EL222, a light-regulated DNA-binding protein. The dark-state crystal structure reveals interactions between the EL222 LOV and helix-turn-helix domains that we show inhibit DNA binding. Solution biophysical data indicate that illumination breaks these interactions, freeing the LOV and helix-turn-helix domains of each other. This conformational change has a key functional effect, allowing EL222 to bind DNA in a light-dependent manner. Our data reveal a conserved signaling mechanism among diverse LOV-containing proteins, where light-induced conformational changes trigger activation via a conserved interaction surface.

Phototropins, a class of light-activated protein kinases, are essential for several blue light responses in plants and algae, including phototropism. These proteins contain two internal light, oxygen, and voltage sensitive (LOV) domains, which bind flavin chromophores and undergo a reversible photochemical formation of a cysteinyl-flavin adduct as part of the light sensing process. While the photodynamic properties of such photosensory domains are dictated by interactions between the chromophore and surrounding protein, more distant residues can play a significant role as well. Here we explore the role of the Phe434 residue in the photosensory response of the second LOV domain of Avena sativa phototropin 1 (AsLOV2), a model photochemical system for these LOV domains. Phe434 is more than 6 Å from the FMN chromophore in AsLOV2; nevertheless, an F434Y point mutation is likely to change several structural features of the chromophore binding site, as we demonstrate using molecular dynamics simulations. Transient absorption signals spanning 15 decades in time were compared for wild-type AsLOV2 and the F434Y mutant, showing that the latter has significantly altered photodynamics, including (i) a faster intersystem crossing leading to triplet formation on a nanosecond time scale, (ii) biphasic formation of adduct-state kinetics on the microsecond time scale, and (iii) greatly accelerated ground-state recovery kinetics on a second time scale. We present mechanistic models that link these spectroscopic differences to changes in the configuration of the critical cysteine residue and in the chromophore's accessibility to solvent and oxygen according to MD trajectories and purging experiments. Taken together, these results demonstrate the importance of residues outside the chromophore-binding pocket in modulating LOV domain photodynamics.

Light is a key stimulus for plant biological functions, several of which are controlled by light-activated kinases known as phototropins, a group of kinases that contain two light-sensing domains (LOV, light-oxygen-voltage domains) and a C-terminal serine/threonine kinase domain. The second sensory domain, LOV2, plays a key role in regulating kinase enzymatic activity via the photochemical formation of a covalent adduct between a LOV2 cysteine residue and an internally bound flavin mononucleotide (FMN) chromophore. Subsequent conformational changes in LOV2 lead to the unfolding of a peripheral Jalpha helix and, ultimately, phototropin kinase activation. To date, the mechanism coupling bond formation and helix dissociation has remained unclear. Previous studies found that a conserved glutamine residue [Q513 in the Avena sativa phototropin 1 LOV2 (AsLOV2) domain] switches its hydrogen bonding pattern with FMN upon light stimulation. Located in the immediate vicinity of the FMN binding site, this Gln residue is provided by the Ibeta strand that interacts with the Jalpha helix, suggesting a route for signal propagation from the core of the LOV domain to its peripheral Jalpha helix. To test whether Q513 plays a key role in tuning the photochemical and transduction properties of AsLOV2, we designed two point mutations, Q513L and Q513N, and monitored the effects on the chromophore and protein using a combination of UV-visible absorbance and circular dichroism spectroscopy, limited proteolysis, and solution NMR. The results show that these mutations significantly dampen the changes between the dark and lit state AsLOV2 structures, leaving the protein in a pseudodark state (Q513L) or a pseudolit state (Q513N). Further, both mutations changed the photochemical properties of this receptor, in particular the lifetime of the photoexcited signaling states. Together, these data establish that this residue plays a central role in both spectral tuning and signal propagation from the core of the LOV domain through the Ibeta strand to the peripheral Jalpha helix.

Objective: Chondrocytes are highly sensitive to variations in extracellular glucose and oxygen levels in the extracellular matrix. As such, they must possess a number of mechanisms to detect and respond to alterations in the metabolic state of cartilage. In other organs such as the pancreas, heart and brain, such detection is partly mediated by a family of potassium channels known as K(ATP) (adenosine 5'-triphosphate-sensitive potassium) channels. Here we investigate whether chondrocytes too express functional K(ATP) channels, which might, potentially, serve to couple metabolic state with cell activity., Methods: Immunohistochemistry was used to explore K(ATP) channel expression in equine and human chondrocytes. Biophysical properties of equine chondrocyte K(ATP) channels were investigated with patch-clamp electrophysiology., Results: Polyclonal antibodies directed against the K(ATP) Kir6.1 subunit revealed high levels of expression in human and equine chondrocytes mainly in superficial and middle zones of normal cartilage. Kir6.1 was also detected in superficial chondrocytes in osteoarthritic (OA) cartilage. In single-channel electrophysiological studies of equine chondrocytes, we found K(ATP) channels to have a maximum unitary conductance of 47 +/- 9 pS (n=5) and a density of expression comparable to that seen in excitable cells., Conclusion: We have shown, for the first time, functional K(ATP) channels in chondrocytes. This suggests that K(ATP) channels are involved in coupling metabolic and electrical activities in chondrocytes through sensing of extracellular glucose and intracellular adenosine triphosphate (ATP) levels. Altered K(ATP) channel expression in OA chondrocytes may result in impaired intracellular ATP sensing and optimal metabolic regulation.