Flunarizine suppresses Mycobacterium tuberculosis growth via calmodulin-dependent phagosome maturation.

Tuberculosis (TB), an infectious bacterial disease caused by Mycobacterium tuberculosis (Mtb), is a major cause of death worldwide. Multidrug-resistant TB remains a public health crisis and thus novel effective treatments, such as host-directed therapies (HDTs), are urgently required to overcome the challenges of TB infection. In this study, we evaluated 4 calcium modulators for their effects on Mtb growth in macrophages. Only flunarizine enhanced the bactericidal ability of macrophages against Mtb, which was induced by an increase in phosphorylated calcium/calmodulin (CaM)-dependent protein kinase II (pCaMKII) levels. We further discovered that the expression of CaM was decreased in Mtb-infected macrophages and restored following flunarizine treatment; this was associated with phagolysosome maturation and acidification. Consistent with these findings, the anti-TB ability of macrophages was reduced following the silencing of CaM or inhibition of CAMKII activity. In conclusion, our results demonstrated that flunarizine enhanced the bactericidal ability of macrophages and clarified its CaM-pCAMKII-dependent mechanism. Therefore, our findings strongly support further studies of this currently approved drug as an HDT candidate for TB therapy.

Flunarizine, a drug approved for treating migraine and vertigo, exhibits cytotoxicity in GBM cells.

Glioblastoma multiforme (GBM) is the most aggressive brain tumor with a poor prognosis. The current treatment regimen, including surgical resection, radiation, and temozolomide (TMZ) chemotherapy, is still not curative. Therefore, there is an emerging need to develop a drug to treat GBM or synergistic enhance TMZ effect on GBM cells. Flunarizine (FLN), a drug approved for treating migraine and vertigo, was analyzed for its cytotoxicity and synergistic effect with TMZ on GBM cells in this study. Cell proliferation, clonogenic assay, flow cytometry, and Western blotting were used to determine the effects of FLN on three GBM cells, U-87 MG, LN-229, and U-118 MG cells. We found that FLN induced GBM cell death. FLN also interfered with U-87 MG cell cycle progression. Flow cytometric analysis showed an increase of apoptotic cells after FLN treatment. Caspase 9, caspase 3, and Poly (ADP-ribose) polymerase (PARP) activation were involved in apoptosis induction in U-87 MG and LN-229, suggesting the possible involvement of an intrinsic apoptotic pathway. We found that FLN treatment inhibited Akt pathway activation in U-87 MG cells, and synergistically increased the cytotoxicity of three GBM cells when combined with TMZ treatment. In conclusion, our current data suggested that FLN inhibited cell viability by inducing apoptosis. FLN inhibited Akt activation and enhanced the sensitivity of GBM cells to TMZ. These findings may provide important information regarding the application of FLN in GBM treatment in the future.

Mibefradil and Flunarizine, Two T-Type Calcium Channel Inhibitors, Protect Mice against Lipopolysaccharide-Induced Acute Lung Injury.

Recent studies have illuminated that blocking Ca2+ influx into effector cells is an attractive therapeutic strategy for lung injury. We hypothesize that T-type calcium channel may be a potential therapeutic target for acute lung injury (ALI). In this study, the pharmacological activity of mibefradil (a classical T-type calcium channel inhibitor) was assessed in a mouse model of lipopolysaccharide- (LPS-) induced ALI. In LPS challenged mice, mibefradil (20 and 40 mg/kg) dramatically decreased the total cell number, as well as the productions of TNF-α and IL-6 in bronchoalveolar lavage fluid (BALF). Mibefradil also suppressed total protein concentration in BALF, attenuated Evans blue extravasation, MPO activity, and NF-κB activation in lung tissue. Furthermore, flunarizine, a widely prescripted antimigraine agent with potent inhibition on T-type channel, was also found to protect mice against lung injury. These data demonstrated that T-type calcium channel inhibitors may be beneficial for treating acute lung injury. The important role of T-type calcium channel in the acute lung injury is encouraged to be further investigated.

Novel pharmacological modulation of dystonic phenotypes caused by a gain-of-function mutation in the Na+ leak-current channel.

The Na leak-current channel (NALCN) regulates the resting membrane potential in excitable cells, thus determining the likelihood of depolarization in response to incoming signals. Gain-of-function (gf) mutations in this channel are associated with severe dystonic movement disorders in man. Currently, there are no known pharmacological antagonists or selective modulators of this important channel. A gain-of-function mutation in NALCN of C. elegans [known as unc-77(e625)] causes uncoordinated, hyperactive locomotion. We hypothesized that this hyperactive phenotype can be rescued with pharmacological modulators. Here, we summarize the results of targeted drug screening aimed at identification of drugs that corrected locomotion deficits in unc-77(e625) animals. To assay hyperactive locomotion, animals were acutely removed from food and characteristic foraging movements were quantified. Drug screening revealed that 2-aminoethoxydiphenyl borate (2-ABP), nifedipine, nimodipine, flunarizine and ethoxzolamide significantly decreased abnormal movements in unc-77(e625) animals. 2-APB also corrected egg release and coiling deficits in this strain. In addition, serotonin and dopamine both reduced hyperactive locomotion, consistent with regulatory interactions between these systems and the NALCN. 2-APB induced movement phenotypes in wild-type animals that faithfully mimicked those observed in NALCN knockout strains, which suggested that this drug may directly block the channel. Moreover, 2-APB and flunarizine showed significant structural similarities suggestive of overlap in their mode of action. Together, these studies have revealed new insights into regulation of NALCN function and led to the discovery of a potential pharmacological antagonist of the NALCN.

Point of View: Electrophysiological Endpoints Differ When Comparing the Mode of Action of Highly Successful Anti-arrhythmic Drugs in the CAVB Dog Model With TdP.

In the anaesthetized, chronic atrioventricular block (CAVB) dog, ventricular ectopic beats and Torsade de pointes arrhythmias (TdP) are believed to ensue from an abrupt prolongation of ventricular repolarization and increased temporal dispersion of repolarization, quantified as short-term variability (STV). These TdP stop spontaneously or, when supported by substantial spatial dispersion of repolarization (SDR), degenerate into ventricular fibrillation. However, most studies involving ventricular arrhythmias do not quantify SDR by means of an electrophysiological parameter. Therefore, we reviewed the effects of 4 highly effective anti-arrhythmic drugs (flunarizine, verapamil, SEA-0400, and GS-458967) on the repolarization duration and associated STV. All drugs were tested as anti-arrhythmic strategies against TdP in CAVB dogs, their high anti-arrhythmic efficacy was defined as suppressing drug-induced TdP in 100% of the experiments. This comparison demonstrates that even though the anti-arrhythmic outcome was similar for all drugs, distinct responses of repolarization duration and associated STV were observed. Moreover, the aforementioned and commonly adopted electrophysiological parameters were not always sufficient in predicting TdP susceptibility, and additional quantification of the SDR proved to be of added value in these studies. The variability in electrophysiological responses to the different anti-arrhythmic drugs and their inconsistent adequacy in reflecting TdP susceptibility, can be explained by distinct modes of interference with TdP development. As such, this overview establishes the separate involvement of temporal and spatial dispersion in ventricular arrhythmogenesis in the CAVB dog model and proposes SDR as an additional parameter to be included in future fundamental and/or pharmaceutical studies regarding TdP arrhythmogenesis.

Inhibition of gap junctional intercellular communication by an anti-migraine agent, flunarizine.

Gap junctions (GJs), which consist of proteins called connexins, are intercellular channels that allow the passage of ions, second messengers, and small molecules. GJs and connexins are considered as emerging therapeutic targets for various diseases. Previously, we screened numerous compounds using our recently developed iodide yellow fluorescent protein gap junctional intercellular communication (I-YFP GJIC) assay and found that flunarizine (FNZ), used for migraine prophylaxis and as an add-on therapy for epilepsy, inhibits GJIC in LN215 human glioma cells. In this study, we confirmed that FNZ inhibits GJIC using the I-YFP GJIC assay. We demonstrated that FNZ inhibits GJ activities via a mechanism that is independent of calcium channels and dopaminergic D2, histaminergic H1, or 5-HT receptors. In addition, we showed that FNZ significantly increases connexin 43 (Cx43) phosphorylation on the cell surface, but does not alter the total amount of Cx43. The beneficial effects of FNZ on migraines and epilepsy might be related to GJ inhibition.

Effect of flunarizine on defibrillation outcomes and early refibrillation in a canine model of prolonged ventricular fibrillation.

NEW FINDINGS: What is the central question of this study? Can successful electrical shock in combination with a delayed after-depolarization (DAD) blocker suppress early refibrillation episodes following long duration ventricular fibrillation (LDVF)? What is the main finding and its importance? Flunarizine significantly reduced the activation of LDVF and early ventricular fibrillation (VF) recurrence following LDVF, suggesting that DADs potentially contribute to refibrillation in prolonged VF. Thus, DAD inhibition can be used as an adjunctive therapy for electrical defibrillation to treat prolonged VF and suppress refibrillation following LDVF. ABSTRACT: This study attempts to detect changes in the defibrillation threshold (DFT) at different stages of ventricular fibrillation (VF) (short duration VF, SDVF; long duration VF, LDVF) and during early refibrillation following successful defibrillation of LDVF by giving flunarizine, a blocker of delayed after-depolarizations (DADs). Twelve beagles were divided into two groups (the control group, n = 6; and the flunarizine group, n = 6). Two 64-electrode basket catheters were deployed into the left and the right ventricles for global endocardium mapping. The DFTs of SDVF and LDVF were determined at 20 s and 7 min, respectively, after VF induction in each group. Any refibrillation episodes were recorded within 15 min after the first successful defibrillation of LDVF. In the flunarizine group, the SDVF-DFT values before and after the drug were not significantly different. The 7 min LDVF-DFTs were markedly reduced by 26% (P < 0.05, the control group) and 38% (P < 0.01, the flunarizine group) compared to the 20 s SDVF-DFTs within each group. The difference between SDVF-DFT and LDVF-DFT after flunarizine was larger than that in the control group (213 ± 65 vs. 120 ± 84 V, P < 0.05). The number of refibrillation episodes per animal (1.3 ± 1.0) following successful defibrillation of LDVF after flunarizine was 48% of that in controls (2.7 ± 2.0, P < 0.05). The effect of flunarizine on SDVF-DFT and LDVF-DFT indicates that the role of DADs in the defibrillation mechanism may differ as VF continues. Flunarizine significantly reduced early VF recurrence following LDVF, suggesting that DADs potentially contribute to refibrillation in a canine model of prolonged VF.

A central hydrophobic E1 region controls the pH range of hepatitis C virus membrane fusion and susceptibility to fusion inhibitors.

BACKGROUND & AIMS: Hepatitis C virus (HCV) infection causes chronic liver disease. Antivirals have been developed and cure infection. However, resistance can emerge and salvage therapies with alternative modes of action could be useful. Several licensed drugs have emerged as HCV entry inhibitors and are thus candidates for drug repurposing. We aimed to dissect their mode of action, identify improved derivatives and determine their viral targets. METHODS: HCV entry inhibition was tested for a panel of structurally related compounds, using chimeric viruses representing diverse genotypes, in addition to viruses containing previously determined resistance mutations. Chemical modeling and synthesis identified improved derivatives, while generation of susceptible and non-susceptible chimeric viruses pinpointed E1 determinants of compound sensitivity. RESULTS: Molecules of the diphenylpiperazine, diphenylpiperidine, phenothiazine, thioxanthene, and cycloheptenepiperidine chemotypes inhibit HCV infection by interfering with membrane fusion. These molecules and a novel p-methoxy-flunarizine derivative with improved efficacy preferentially inhibit genotype 2 viral strains. Viral residues within a central hydrophobic region of E1 (residues 290-312) control susceptibility. At the same time, viral features in this region also govern pH-dependence of viral membrane fusion. CONCLUSIONS: Small molecules from different chemotypes related to flunarizine preferentially inhibit HCV genotype 2 membrane fusion. A hydrophobic region proximal to the putative fusion loop controls sensitivity to these drugs and the pH range of membrane fusion. An algorithm considering viral features in this region predicts viral sensitivity to membrane fusion inhibitors. Resistance to flunarizine correlates with more relaxed pH requirements for fusion. LAY SUMMARY: This study describes diverse compounds that act as HCV membrane fusion inhibitors. It defines viral properties that determine sensitivity to these molecules and thus provides information to identify patients that may benefit from treatment with membrane fusion inhibitors.

Flunarizine for Headache Prophylaxis in Children With Sturge-Weber Syndrome.

BACKGROUND: Children with Sturge-Weber syndrome can experience severe headache with or without transient hemiparesis. Flunarizine, a calcium antagonist, has been used for migraine. The experience with flunarizine for headache in a cohort of children at a national center for Sturge-Weber syndrome is reviewed, reporting its efficacy and adverse effect in this population. METHODS: We collected data from health care professionals' documentation on headache (severity, frequency, duration) before and on flunarizine in 20 children with Sturge-Weber syndrome. Adverse effects reported during flunarizine treatment were collated. The Wilcoxon signed rank test was used to determine the significance of pre- versus post-treatment effect. RESULTS: Flunarizine was used for headache alone (13) or mixed migrainous episodes and vascular events (7). The median duration of treatment was 145 days (range 43 to 1864 days). Flunarizine reduced headache severity (z = -3.354, P = 0.001), monthly frequency (z = -2.585, P = 0.01), and duration (z = -2.549, P = 0.01). Flunarizine was discontinued owing to intolerable adverse effects in a minority (2). Sedation and weight gain were the most common side effects. There were no reports of behavior change or extrapyramidal features. CONCLUSIONS: The most effective management for headaches in patients with Sturge-Weber syndrome has not been established. This retrospective observational study found benefit of flunarizine prophylaxis on headache severity, frequency, and duration in children with Sturge-Weber syndrome without severe side effects. Flunarizine is not licensed for use in the United Kingdom, but these data support its off-license specialist use for headache prophylaxis in Sturge-Weber syndrome.

Induction of N-Ras degradation by flunarizine-mediated autophagy.

Ras GTPases are powerful drivers for tumorigenesis, but directly targeting Ras for treating cancer remains challenging. The growth and transforming activity of the aggressive basal-like breast cancer (BLBC) are driven by N-Ras. To target N-Ras in BLBC, this study screened existing pharmacologically active compounds for the new ability to induce N-Ras degradation, which led to the identification of flunarizine (FLN), previously approved for treating migraine and epilepsy. The FLN-induced N-Ras degradation was not affected by a 26S-proteasome inhibitor. Rather, it was blocked by autophagy inhibitors. Furthermore, N-Ras can be seen co-localized with active autophagosomes upon FLN treatment, suggesting that FLN alters the autophagy pathway to degrade N-Ras. Importantly, FLN treatment recapitulated the effect of N-RAS silencing in vitro by selectively inhibiting the growth of BLBC cells, but not that of breast cancer cells of other subtypes. In addition, in vivo FLN inhibited tumor growth of a BLBC xenograft model. In conclusion, this proof-of-principle study presents evidence that the autophagy pathway can be coerced by small molecule inhibitors, such as FLN, to degrade Ras as a strategy to treat cancer. FLN has low toxicity and should be further investigated to enrich the toolbox of cancer therapeutics.

Role of voltage-gated calcium channels on striatal dopamine release induced by inorganic mercury in freely moving rats.

The possible role of voltage-sensitive calcium channels (VSCC) activation on the HgCl2-induced dopamine release was investigated using selective VSCC blockers and the dopamine levels were measured by HPLC from samples obtained by in vivo brain microdialysis. Infusion of HgCl2 in nicardipine (10 or 100 µM) or flunaricine (10 µM) pretreated animals had no significant effect on dopamine release induced by HgCl2. Pretreatment with 100 µM flunaricine, 20 µM ω-conotoxin MVIIC, or ω-conotoxin GVIA significantly decreased the HgCl2-induced dopamine release over 61%, 88%, and 99%, respectively. HgCl2-induced dopamine release could be produced, at least in part, by activation of VSCC at dopaminergic terminals, especially N- and P/Q-type.

Small-molecule flunarizine increases SMN protein in nuclear Cajal bodies and motor function in a mouse model of spinal muscular atrophy.

The hereditary neurodegenerative disorder spinal muscular atrophy (SMA) is characterized by the loss of spinal cord motor neurons and skeletal muscle atrophy. SMA is caused by mutations of the survival motor neuron (SMN) gene leading to a decrease in SMN protein levels. The SMN deficiency alters nuclear body formation and whether it can contribute to the disease remains unclear. Here we screen a series of small-molecules on SMA patient fibroblasts and identify flunarizine that accumulates SMN into Cajal bodies, the nuclear bodies important for the spliceosomal small nuclear RNA (snRNA)-ribonucleoprotein biogenesis. Using histochemistry, real-time RT-PCR and behavioural analyses in a mouse model of SMA, we show that along with the accumulation of SMN into Cajal bodies of spinal cord motor neurons, flunarizine treatment modulates the relative abundance of specific spliceosomal snRNAs in a tissue-dependent manner and can improve the synaptic connections and survival of spinal cord motor neurons. The treatment also protects skeletal muscles from cell death and atrophy, raises the neuromuscular junction maturation and prolongs life span by as much as 40 percent (p < 0.001). Our findings provide a functional link between flunarizine and SMA pathology, highlighting the potential benefits of flunarizine in a novel therapeutic perspective against neurodegenerative diseases.

Role of flunarizine hydrochloride in secondary brain injury following intracerebral hemorrhage in rats.

This study aimed to explore the role and mechanism(s) of flunarizine hydrochloride in the intracerebral hemorrhage (ICH) rats. The 32 adult male Sprague Dawley (SD) rats were randomly assigned into four groups: control group, sham group, ICH group, and FLU + ICH group. The effects of flunarizine hydrochloride were assessed on the basis of hematoma volume, blood-brain barrier (BBB) integrity, and brain water content in the ICH rat models. The role of flunarizine hydrochloride in cell recovery was assessed by behavioral scores, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot assay. Involvement of PI3K/AKT pathway in exerting the effect of flunarizine hydrochloride was also determined. Results showed that the hematoma volume, BBB integrity, and brain water content were significantly decreased in the FLU + ICH group. Cell apoptosis significantly increased in the ICH model group, while flunarizine hydrochloride decreased this increase. The expressions of glial cell line-derived neurotrophic factor (GDNF), neuroglobin (NGB), and p-AKT were increased after flunarizine hydrochloride treatment in ICH rats. In conclusion, flunarizine hydrochloride has protective effects against ICH by reducing brain injury, cell apoptosis, and the activation of P13K/AKT pathway. These findings provide a theoretical basis for the treatment of flunarizine hydrochloride in ICH.

Flunarizine suppresses endothelial Angiopoietin-2 in a calcium - dependent fashion in sepsis.

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to an infection leading to systemic inflammation and endothelial barrier breakdown. The vascular-destabilizing factor Angiopoietin-2 (Angpt-2) has been implicated in these processes in humans. Here we screened in an unbiased approach FDA-approved compounds with respect to Angpt-2 suppression in endothelial cells (ECs) in vitro. We identified Flunarizine - a well-known anti-migraine calcium channel (CC) blocker - being able to diminish intracellular Angpt-2 protein in a time- and dose-dependent fashion thereby indirectly reducing the released protein. Moreover, Flunarizine protected ECs from TNFα-induced increase in Angpt-2 transcription and vascular barrier breakdown. Mechanistically, we could exclude canonical Tie2 signalling being responsible but found that three structurally distinct T-type - but not L-type - CC blockers can suppress Angpt-2. Most importantly, experimental increase in intracellular calcium abolished Flunarizine's effect. Flunarizine was also able to block the injurious increase of Angpt-2 in murine endotoxemia in vivo. This resulted in reduced pulmonary adhesion molecule expression (intercellular adhesion molecule-1) and tissue infiltration of inflammatory cells (Gr-1). Our finding could have therapeutic implications as side effects of Flunarizine are low and specific sepsis therapeutics that target the dysregulated host response are highly desirable.

Flunarizine rescues reduced lifespan in CLN3 triple knock-out Caenorhabditis elegans model of batten disease.

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease, previously known as classic juvenile neuronal ceroid lipofuscinosis, NCL) is a pediatric-onset progressive neurodegenerative disease characterized by progressive vision loss, seizures, loss of cognitive and motor function, and early death. While no precise biochemical mechanism or therapies are known, the pathogenesis of CLN3 disease involves intracellular calcium accumulation that may trigger apoptosis. Our prior work in in vitro cell models of CLN3 deficiency suggested that FDA-approved calcium channel antagonists may have therapeutic value. To further evaluate the potential efficacy of this approach in an otherwise untreatable disorder, we sought to compare the therapeutic effects and underlying mechanisms in an animal model of CLN3 disease. Here, we used the well-characterized XT7 complete cln-3 knockout strain of C. elegans to evaluate the therapeutic efficacy of calcium channel antagonist therapy in a living animal model of Batten disease. Therapeutic effects of five calcium channel antagonists were evaluated on XT7 animal lifespan and in vivo mitochondrial physiology. Remarkably, maximal therapeutic efficacy in this model animal was observed with 1 µM flunarizine, the identical concentration previously identified in cell-based neuronal models of CLN3 disease. Specifically, flunarizine rescued the short lifespan of XT7 worms and prevented their pathophysiologic mitochondrial accumulation. These results confirm the treatment efficacy and dosing of flunarizine in cln-3 disease in a translational model organism. Clinical treatment trials in CLN3 human patients are now needed to test the dosing regimen and efficacy of flunarizine in individuals suffering with this otherwise untreatable and ultimately lethal neurologic disease.

Flunarizine prevents hepatitis C virus membrane fusion in a genotype-dependent manner by targeting the potential fusion peptide within E1.

UNLABELLED: To explore mechanisms of hepatitis C viral (HCV) replication we screened a compound library including licensed drugs. Flunarizine, a diphenylmethylpiperazine used to treat migraine, inhibited HCV cell entry in vitro and in vivo in a genotype-dependent fashion. Analysis of mosaic viruses between susceptible and resistant strains revealed that E1 and E2 glycoproteins confer susceptibility to flunarizine. Time of addition experiments and single particle tracking of HCV demonstrated that flunarizine specifically prevents membrane fusion. Related phenothiazines and pimozide also inhibited HCV infection and preferentially targeted HCV genotype 2 viruses. However, phenothiazines and pimozide exhibited improved genotype coverage including the difficult to treat genotype 3. Flunarizine-resistant HCV carried mutations within the alleged fusion peptide and displayed cross-resistance to these compounds, indicating that these drugs have a common mode of action. CONCLUSION: These observations reveal novel details about HCV membrane fusion; moreover, flunarizine and related compounds represent first-in-class HCV fusion inhibitors that merit consideration for repurposing as a cost-effective component of HCV combination therapies.

Flunarizine exhibits in vitro efficacy against lymphoma and multiple myeloma cells.

BACKGROUND/AIM: Novel agents such as lenalidomide and bortezomib have significantly improved today's therapy of multiple myeloma. Despite recent innovations, new therapeutic options are needed. The Wingless-related integration site (WNT) pathway is aberrantly activated in lymphoma and myeloma and therefore renders WNT signaling molecules attractive for the development of targeted therapies. Flunarizine was used in this study as it has chemical features similar to those of other known WNT inhibitors and already proven proapoptotic properties in leukemia cells. MATERIALS AND METHODS: The antitumor apoptotic effect of flunarizine at doses ranging from 0.1-200 µM was investigated on three human lymphoma cell lines, one murine and four human myeloma cell lines by 3'3-Dihexyloxacarbocyanine iodide and propidium iodide staining in flow cytometry. RESULTS: Flunarizine induced significant apoptotic activity in all tested myeloma and lymphoma cell lines in a dose-dependent manner. CONCLUSION: Our results reveal a significant selective induction of apoptosis by flunarizine and suggest an in vivo effect against lymphoma and myeloma.

Investigation of the role of non-selective calcium channel blocker (flunarizine) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice.

The present study was designed to investigate the role of flunarizine (a non-selective calcium channel blocker) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice. Bilateral carotid artery occlusion of 12min followed by reperfusion for 24h was given to induce cerebral injury in male Swiss mice. The assessment of learning & memory was performed by Morris water maze test; motor in-coordination was evaluated by rota rod, lateral push and inclined beam walking tests; cerebral infarct size was quantified by triphenyltetrazolium chloride staining. In addition, reduced glutathione (GSH), total calcium and acetylcholinesterase (AChE) activity were also estimated in aged brain tissue. Donepezil treated group served as a positive control in this study. Ischemia reperfusion (I/R) injury produced significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Further, I/R injury also produced significant increase in levels of total calcium, AChE activity and decrease in GSH levels. Pretreatment of flunarizine significantly attenuated I/R induced infarct size, behavioral and biochemical changes. Hence, it may be concluded that, a non-selective calcium channel blocker can be useful in I/R associated cognitive dysfunction due to its anti-oxidant, anti-infarct and modulatory actions of neurotransmitters & calcium channels.

AV-block and conduction slowing prevail over TdP arrhythmias in the methoxamine-sensitized pro-arrhythmic rabbit model.

INTRODUCTION: The methoxamine-sensitized rabbit model is widely used to screen drugs for proarrhythmic properties, especially repolarization-dependent TdP arrhythmias. With the change of anesthesia and/or sensitizing agent, conduction disturbances have been reported as well. Therefore, we compared currently available in-house anesthetics in order to preserve arrhythmia sensitivity and preclude conduction disturbances. METHODS AND RESULTS: Rabbits were randomly assigned to 3 groups: (1) 35 mg/kg ketamine + 5 mg/kg xylazine; (2) 0.5 mL/kg hypnorm + 3 mg/kg midazolam; (3) 35 mg/kg ketamine + 20 mg/kg propofol. Anesthesia was maintained by 1.5% isoflurane. Concomitant infusion of methoxamine (17 µg/kg/min for 40 minutes) and dofetilide (10 µg/kg/min for 30 minutes) was used to induce arrhythmias. Sole methoxamine infusion exclusively decreased HR in groups 1 and 3. Dofetilide lengthened repolarization, followed in time by PQ/QRS prolongation, second-degree AV block, and subsequently TdP arrhythmias. TdP was seen in 80%, 0%, and 33% of the rabbits in groups 1, 2, and 3, respectively. Decreasing the dose of dofetilide to 5 µg/kg/min in ketamine/xylazine anesthetized rabbits resulted in a drop in TdP incidence (25%) while conduction disturbances persisted. Flunarizine (n = 6) suppressed all TdP arrhythmias while conduction disturbances remained present. CONCLUSION: TdP incidence in the methoxamine-sensitized rabbit could be dramatically influenced by anesthesia, drug dose, and flunarizine, while conduction slowing remained present. Thus, conduction slowing seems to be the integral outcome in this model.