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1.  Interleukin-1beta Causes Fluoxetine Resistance in an Animal Model of Epilepsy-Associated Depression 
Neurotherapeutics  2012;9(2):477-485.
Depression represents a common comorbidity of epilepsy and is frequently resistant to selective serotonin reuptake inhibitors (SSRI). We tested the hypothesis that the SSRI resistance in epilepsy associated depression may be a result of a pathologically enhanced interleukin-1β (IL1-β) signaling, and consequently that the blockade of IL1-β may restore the effectiveness of SSRI. Epilepsy and concurrent depression-like impairments were induced in Wistar rats by pilocarpine status epilepticus (SE). The effects of the 2-week long treatment with fluoxetine, interleukin-1 receptor antagonist (IL-1ra), and their combination were examined using behavioral, biochemical, neuroendocrine, and autoradiographic assays. In post-SE rats, depression-like impairments included behavioral deficits indicative of hopelessness and anhedonia; the hyperactivity of the hypothalamo-pituitary-adrenocortical axis; the diminished serotonin output from raphe nucleus; and the upregulation of presynaptic serotonin 1-A (5-HT1A) receptors. Fluoxetine monotherapy exerted no antidepressant effects, whereas the treatment with IL-1ra led to the complete reversal of anhedonia and to a partial improvement of all other depressive impairments. Combined administration of fluoxetine and IL-1ra completely abolished all hallmarks of epilepsy-associated depressive abnormalities, with the exception of the hyperactivity of the hypothalamo-pituitary-adrenocortical axis, the latter remaining only partially improved. We propose that in certain forms of depression, including but not limited to depression associated with epilepsy, the resistance to SSRI may be driven by the pathologically enhanced interleukin-1β signaling and by the subsequent upregulation of presynaptic 5-HT1A receptors. In such forms of depression, the use of interleukin-1β blockers in conjunction with SSRI may represent an effective therapeutic approach.
Electronic supplementary material
The online version of this article (doi:10.1007/s13311-012-0110-4) contains supplementary material, which is available to authorized users.
doi:10.1007/s13311-012-0110-4
PMCID: PMC3337012  PMID: 22427156
Epilepsy; depression; comorbidity; cytokines; selective serotonin reuptake inhibitors
2.  High-mobility group box-1 impairs memory in mice through both toll-like receptor 4 and Receptor for Advanced Glycation End Products 
Experimental neurology  2011;232(2):143-148.
High-mobility group box-1 (HMGB1) is a nuclear protein with cytokine-type functions upon its extracellular release. HMGB1 activates inflammatory pathways by stimulating multiple receptors, chiefly toll-like receptor 4 (TLR4) and Receptor for Advanced Glycation End Products (RAGE). TLR4 and RAGE activation has been implicated in memory impairments, although the endogenous ligand subserving these effects is unknown. We examined whether HMGB1 induced memory deficits using novel object recognition test, and which of the two receptor pathways was involved in these effects. Non-spatial long-term memory was examined in wild type, TLR4 knockout, and RAGE knockout mice. Recombinant HMGB1 (10 μg, intracerebroventricularly, i.c.v.) disrupted memory encoding equipotently in wild type, TLR4 knockout and RAGE knockout animals, but affected neither memory consolidation, nor retrieval. Neither TLR4 knockout nor RAGE knockout mice per se, exhibited memory deficits. Blockade of TLR4 in RAGE knockout mice using Rhodobacter sphaeroides lipopolysaccharide (LPS-Rs; 20 μg, i.c.v.) prevented the detrimental effect of HMGB1 on memory. These data show that elevated brain levels of HMGB1 induce memory abnormalities which may be mediated by either TLR4, or RAGE. This mechanism may contribute to memory deficits under various neurological and psychiatric conditions associated with the increased HMGB1 levels, such as epilepsy, Alzeheimer’s disease and stroke.
doi:10.1016/j.expneurol.2011.08.012
PMCID: PMC3202022  PMID: 21884699
Inflammation; High-mobility group box-1; toll-like receptor 4; Receptor for Advanced Glycation End Products; memory; novel object recognition test
3.  Plasticity of Presynaptic and Postsynaptic Serotonin 1A Receptors in an Animal Model of Epilepsy-Associated Depression 
Neuropsychopharmacology  2011;36(6):1305-1316.
Depression is a common comorbidity of temporal lobe epilepsy and has highly negative impact on patients' quality of life. We previously established that pilocarpine-induced status epilepticus (SE) in rats, concurrently with chronic epilepsy leads to depressive impairments, and that the latter may stem from the dysregulation of hypothalamo–pituitary–adrenocortical (HPA) axis and/or diminished raphe–hippocampal serotonergic transmission. We examined possible involvement of presynaptic and postsynaptic serotonin 1A (5-HT1A) receptors in epilepsy-associated depression. Based on their performance in the forced swim test (FST), post-SE animals were classified as those with moderate and severe depressive impairments. In moderately impaired rats, the activity of the HPA axis (examined using plasma corticosterone radioimmunoassay) was higher than in naive subjects, but the functional capacity of presynaptic 5-HT1A receptors (measured in raphe using autoradiography) remained unaltered. In severely depressed animals, both the activity of the HPA axis and the function of presynaptic 5-HT1A receptors were increased as compared with naive and moderately depressed rats. Pharmacological uncoupling of the HPA axis from raphe nucleus exerted antidepressant effects in severely impaired rats, but did not modify behavior in both naive and moderately depressed animals. Further, the function of postsynaptic 5-HT1A receptors was diminished in the hippocampus of post-SE rats. Pharmacological activation of postsynaptic 5-HT1A receptors improved depressive deficits in epileptic animals. We suggest that under the conditions of chronic epilepsy, excessively hyperactive HPA axis activates presynaptic 5-HT1A receptors, thus shifting the regulation of serotonin release in favor of autoinhibition. Downregulation of postsynaptic 5-HT1A receptors may further exacerbate the severity of epilepsy-associated depression.
doi:10.1038/npp.2011.18
PMCID: PMC3077437  PMID: 21346733
epilepsy; depression; comorbidity; serotonin 1A receptors; dorsal raphe; hypothalamo–pituitary–adrenocortical axis; mood / anxiety / stress disorders; serotonin; animal models; neurology; epilepsy; comorbidity; dorsal aphe; hippocampus; serotonin 1A receptors
4.  Plasticity of presynaptic and postsynaptic serotonin 1A receptors in an animal model of epilepsy – associated depression 
Depression is a common comorbidity of temporal lobe epilepsy and has highly negative impact on patients’ quality of life. We previously established that pilocarpine-induced status epilepticus (SE) in rats, concurrently with chronic epilepsy leads to depressive impairments, and that the latter may stem from the dysregulation of hypothalamo-pituitary-adrenocortical (HPA) axis and/or diminished raphe-hippocampal serotonergic transmission. We examined possible involvement of presynaptic and postsynaptic serotonin-1A (5-HT1A) receptors in epilepsy-associated depression. Based on their performance in the forced swim test (FST), post-SE animals were classified as those with moderate and severe depressive impairments. In moderately impaired rats, the activity of the HPA axis (examined using plasma corticosterone radioimmunoassay) was higher than in naïve subjects, but the functional capacity of presynaptic 5-HT1A receptors (measured in raphe using autoradiography) remained unaltered. In severely depressed animals, both the activity of the HPA axis and the function of presynaptic 5-HT1A receptors were increased as compared with naïve and moderately depressed rats. Pharmacological uncoupling of the HPA axis from raphe nucleus exerted antidepressant effects in severely impaired rats, but did not modify behavior in both naïve and moderately depressed animals. Further, the function of postsynaptic 5-HT1A receptors was diminished in the hippocampus of post-SE rats. Pharmacological activation of postsynaptic 5-HT1A receptors improved depressive deficits in epileptic animals. We suggest that under conditions of chronic epilepsy, excessively hyperactive HPA axis activates presynaptic 5-HT1A receptors, thus shifting the regulation of serotonin release in favor of autoinhibition. Downregulation of postsynaptic 5-HT1A receptors may further exacerbate the severity of epilepsy-associated depression.
doi:10.1038/npp.2011.18
PMCID: PMC3077437  PMID: 21346733
Epilepsy; depression; comorbidity; serotonin 1A receptors; dorsal raphe; hypothalamo-pituitary-adrenocortical axis
5.  Evaluation of development-specific targets for antiepileptogenic therapy using rapid kindling 
Epilepsia  2010;51(Suppl 3):39-42.
We used the method of rapid hippocampal kindling to assess the potential antiepileptogenic efficacy of a number of anticonvulsant medications. This method afforded a higher throughput than methods based on traditional kindling or post-status epilepticus models of epileptogenesis. This “compressed epileptogenesis” model also permitted the study of age-dependent pharmacologic targets, and distinguished among AEDs based on their age-specific antiepileptogenic efficacy. We found retigabine to be the most effective anticonvulsant therapy during early development. Topiramate seemed most effective further along development, while some drugs did not demonstrate an age-specific effect. The method also reproduced some of the paradoxical pharmacologic findings previously shown with lamotrigine. While the utility of this model for screening the antiepileptogenic therapies requires further validation it introduces the ability to undertake development-specific testing and a more rapid throughput than conventional methods.
doi:10.1111/j.1528-1167.2010.02607.x
PMCID: PMC2912152  PMID: 20618398
Epileptogenesis; development; rapid kindling; hippocampus
6.  Bumetanide inhibits rapid kindling in neonatal rats 
Epilepsia  2009;50(9):2117-2122.
Purpose
To examine effects of bumetanide, a selective blocker of Na+-K+-2Cl− cotransporter (NKCC1), on hippocampal excitability and rapid kindling in immature rats.
Methods
Studies were performed in Wistar rats of three ages: postnatal day 11 (P11, neonatal), P14 (post-neonatal), and P21 (pre-adolescent). Bumetanide (0.2, 0.5, 2.5 mg/kg) was given intraperitoneally 20 minutes prior to the beginning of the studies. Hippocampal excitability was examined by measuring threshold and duration of afterdischarge, which had been elicited by electrical stimulation of ventral hippocampus. Kindling procedure consisted of 80 electrical stimulations of ventral hippocampus, delivered every 5 minutes.
Results
At P11, bumetanide (0.5 mg/kg) increased the baseline hippocampal afterdischarge threshold and shortened the afterdischarge duration. Bumetanide delayed the occurrence, and reduced the number of full motor seizures during kindling, and prevented the development of kindling-induced enhanced seizure susceptibility in a majority of animals. At P14 bumetanide (0.5 mg/kg) induced no significant antiepileptic effects, although suppression of hippocampal excitability and inhibition of kindling were observed in a subset of animals. At P21 bumetanide (0.2; 2.5 mg/kg) exerted no effects on hippocampal excitability and kindling progression.
Discussion
The obtained results provide further evidence that bumetanide may be beneficial for treating neonatal seizures, and that NKCC1 represents a potential target for antiepileptic interventions in the immature brain.
doi:10.1111/j.1528-1167.2009.02048.x
PMCID: PMC2732750  PMID: 19260939
Epilepsy; kindling; Na+-K+-2Cl− cotransporter; bumetanide
7.  Antiepileptogenic and antiictogenic effects of retigabine under conditions of rapid kindling: an ontogenic study 
Epilepsia  2008;49(10):1777-1786.
SUMMARY
Purpose
To examine antiepileptogenic and antiictogenic potential of retigabine under conditions of rapid kindling epileptogenesis during different stages of development.
Methods
The experiments were performed in postnatal day 14 (P14), P21 and P35 male Wistar rats. After stereotaxic implantation of hippocampal stimulating and recording electrodes, the effects of retigabine on baseline afterdischarge properties were studied. Next, the animals underwent rapid kindling (sixty 10 second trains, bipolar 20 Hz square wave pulses delivered every five minutes). The progression of seizures (kindling acquisition), and responses to test stimulations after kindling (retention) were compared between retigabine and vehicle-treated rats. Additionally, the effects of retigabine on the severity of seizures in previously kindled animals were examined.
Results
When administered intraperitoneally in doses that induced only mild, or no motor deficits, retigabine significantly dampened brain excitability, evident as the increase of afterdischarge threshold and shortening of afterdischarge duration. During kindling, retigabine delayed the development of focal seizures in P14 rats, and prevented the occurrence of full limbic seizures at all three ages. At P14 and P21, but not at P35, pretreatment with retigabine prevented the establishment of kindling-induced enhanced seizure susceptibility. Administration of retigabine to kindled animals decreased the severity of seizures induced by test stimulation. The effect was most prominent at P14.
Discussion
Retigabine exerted both antiepileptogenic and antiictogenic effects under conditions of rapid kindling model. These effects were apparent during post-neonatal, early childhood and adolescent stages of development.
doi:10.1111/j.1528-1167.2008.01674.x
PMCID: PMC2577127  PMID: 18503560
Antiepileptic drugs; development; epileptogenesis; kindling; retigabine
8.  Depression after status epilepticus: behavioural and biochemical deficits and effects of fluoxetine 
Brain  2008;131(8):2071-2083.
Depression represents one of the most common comorbidities in patients with epilepsy. However, the mechanisms of depression in epilepsy patients are poorly understood. Establishment of animal models of this comorbidity is critical for both understanding the mechanisms of the condition, and for preclinical development of effective therapies. The current study examined whether a commonly used animal model of temporal lobe epilepsy (TLE) is characterized by behavioural and biochemical alterations involved in depression. Male Wistar rats were subjected to LiCl and pilocarpine status epilepticus (SE). The development of chronic epileptic state was confirmed by the presence of spontaneous seizures and by enhanced brain excitability. Post-SE animals exhibited increase in immobility time under conditions of forced swim test (FST) which was indicative of despair-like state, and loss of taste preference in saccharin solution consumption test which pointed to the symptomatic equivalence of anhedonia. Biochemical studies revealed compromised serotonergic transmission in the raphe-hippocampal serotonergic pathway: decrease of serotonin (5-HT) concentration and turnover in the hippocampus, measured by high performance liquid chromatography, and decrease of 5-HT release from the hippocampus in response to raphe stimulation, measured by fast cyclic voltammetry. Administration of fluoxetine (FLX, 20 mg/kg/day for 10 days) to naive animals significantly shortened immobility time under conditions of FST, and inhibited 5-HT turnover in the hippocampus. In post-SE rats FLX treatment led to a further decrease of hippocampal 5-HT turnover; however, performance in FST was not improved. At the same time, FLX reversed SE-induced increase in brain excitability. In summary, our studies provide initial evidence that post-SE model of TLE might serve as a model of the comorbidity of epilepsy and depression. The finding that behavioural equivalents of depression were resistant to an antidepressant medication suggested that depression in epilepsy might have distinct underlying mechanisms beyond alterations in serotonergic pathways.
doi:10.1093/brain/awn117
PMCID: PMC2587254  PMID: 18559371
comorbidity; depression; epilepsy; hippocampus; serotonin
9.  Depression after status epilepticus: behavioral and biochemical deficits, and effects of fluoxetine 
Brain : a journal of neurology  2008;131(Pt 8):2071-2083.
Summary
Depression represents one of the most common comorbidities in patients with epilepsy. However, the mechanisms of depression in epilepsy patients are poorly understood. Establishment of animal models of this comorbidity is critical for both understanding the mechanisms of the condition, and for preclinical development of effective therapies. The current study examined whether a commonly used animal model of temporal lobe epilepsy (TLE) is characterized by behavioral and biochemical alterations involved in depression. Male Wistar rats were subjected to LiCl and pilocarpine status epilepticus (SE). The development of chronic epileptic state was confirmed by the presence of spontaneous seizures and by enhanced brain excitability. Post-SE animals exhibited increase in immobility time under conditions of forced swim test (FST) which was indicative of despair-like state, and loss of taste preference in saccharin solution consumption test which pointed to the symptomatic equivalence of anhedonia. Biochemical studies revealed compromised serotonergic transmission in the raphe-hippocampal serotonergic pathway: decrease of serotonin (5-HT) concentration and turnover in the hippocampus, measured by high performance liquid chromatography, and decrease of 5-HT release from the hippocampus in response to raphe stimulation, measured by fast cyclic voltammetry. Administration of fluoxetine (FLX, 20 mg/kg/day for 10 days) to naïve animals significantly shortened immobility time under conditions of FST, and inhibited 5-HT turnover in the hippocampus. In post-SE rats FLX treatment led to a further decrease of hippocampal 5-HT turnover; however, performance in FST was not improved. At the same time, FLX reversed SE-induced increase in brain excitability. In summary, our studies provide initial evidence that post-SE model of TLE might serve as a model of the comorbidity of epilepsy and depression. The finding that behavioral equivalents of depression were resistant to an antidepressant medication suggested that depression in epilepsy might have distinct underlying mechanisms beyond alterations in serotonergic pathways.
doi:10.1093/brain/awn117
PMCID: PMC2587254  PMID: 18559371
Comorbidity; depression; epilepsy; hippocampus; serotonin
10.  Age-Dependent Effects of Topiramate on the Acquisition and the Retention of Rapid Kindling 
Epilepsia  2007;48(4):765-773.
Summary
Purpose
To examine antiepileptogenic, disease-modifying, and anticonvulsant effects of topiramate under conditions of rapid kindling at different stages of development.
Methods
Afterdischarge threshold (ADT) and duration (ADD) were examined in two-, three-, and five-week old Wistar rats before and after administration of topiramate (200 mg/kg). Animals underwent a rapid kindling protocol (sixty 10 second trains, bipolar 20 Hz square wave pulses delivered every five minutes). The progression of behavioral and electrographic seizures, and responses to test stimulations 24 hours after the protocol were compared between topiramate and vehicle treated control rats. In addition, rats that were previously given vehicle only prior to kindling, were then given topiramate to examine the effect on established kindled seizures.
Results
In two-week old animals, topiramate affected neither the baseline afterdischarge, nor the progression of kindled seizures. In three-week old rats, topiramate did not modify the baseline afterdischarge, but significantly delayed the occurrence of full motor seizures in response to repeated stimulations. Topiramate treatment of five-week old rats increased baseline ADT, shortened ADD, and delayed the progression of kindled seizures. Twenty four hours after the last kindling stimulation, animals of all ages exhibited a decreased ADT, an increase ADD, and developed behavioral seizures in response to threshold stimulation. Vehicle treated kindled rats that were then given topiramate displayed significantly attenuated behavioral seizures induced by the threshold stimulation.
Conclusions
Topiramate exhibited age-dependent disease-modifying effects under conditions of rapid kindling, but failed to block epileptogenesis. Topiramate also inhibited kindled seizures with equal efficacy across the three ages.
doi:10.1111/j.1528-1167.2007.00987.x
PMCID: PMC2376752  PMID: 17319916
Temporal lobe epilepsy; epileptogenesis; kindling; topiramate; antiepileptic drugs; development
11.  Kindling epileptogenesis in immature rats leads to persistent depressive behavior 
Epilepsy & behavior : E&B  2007;10(3):377-383.
Depression is a frequent comorbidity in epilepsy patients. A variety of biological factors may underlie epilepsy-associated depression. We examined whether kindling-induced chronic increase in seizure susceptibility is accompanied by behavioral symptoms of depression. Three week-old Wistar rats underwent rapid kindling - 84 initially subconvulsant electrical stimulations of ventral hippocampus delivered every five minutes - followed by depression-specific behavioral tests performed two and four weeks later. Kindled animals exhibited sustained increase in the immobility time in the forced swim test and the loss of taste preference towards calorie-free saccharin, as compared to controls. Initial loss of preference towards the intake of calorie-containing sucrose was followed by the increased consumption at four weeks. At both time points, animals exhibited enhanced seizure susceptibility upon test stimulations of the hippocampus. We conclude that neuronal plastic changes associated with kindling state are accompanied by the development of depressive behavior.
doi:10.1016/j.yebeh.2007.02.001
PMCID: PMC1958957  PMID: 17368107
Epilepsy; depression; kindling; forced swim test; taste preference; rat
12.  Regulation of kindling epileptogenesis by hippocampal galanin type 1 and type 2 receptors: the effects of subtype selective agonists and the role of G-protein mediated signaling. 
Search for antiepileptic drugs which are capable of blocking the progression of epilepsy (epileptogenesis) is an important problem of translational epilepsy research. The neuropeptide galanin effectively suppresses acute seizures. We examined the ability of hippocampal galanin receptor type 1 (GalR1) and 2 (GalR2) to inhibit kindling epileptogenesis, and studied signaling cascades that mediate their effects. Wistar rats received 24 hour long intrahippocampal infusion of a GalR1/2 agonist galanin(1-29), GalR1 agonist M617, or GalR2 agonist galanin(2-11). The peptides were administered alone, or combined with an inhibitor of Gi protein pertussis toxin (PTX), Gi-protein activated K+ channels (GIRK) inhibitor tertiapin Q (TPQ), Gq/11 protein inhibitor [D-Arg1,D-Trp5,7,9,Leu11]-substance P (dSP), or an inhibitor of intracellular Ca2+ release dantrolene. Sixteen hours into drug delivery, the animals were subjected to rapid kindling - sixty electrical trains administered to ventral hippocampus every 5 minutes. M617 delayed epileptogenesis, while galanin(1-29) and galanin(2-11) completely prevented the occurrence of full kindled seizures. TPQ abolished anticonvulsant effect of M617, but not of galanin(2-11). PTX blocked anticonvulsant effects of M617 and inversed the action of galanin(1-29) and galanin(2-11) to proconvulsant. dSP and dantrolene did not modify seizure suppression through GalR1 and GalR2, but eliminated proconvulsant effect of PTX+galanin(1-29) and PTX+galanin(2-11) combinations. We conclude that hippocampal GalR1 exert disease - modifying effect through Gi-GIRK pathway. GalR2 is antiepileptogenic through Gi mechanism independent of GIRK. Secondary proconvulsant pathway coupled to GalR2, involves Gq/11 and intracellular Ca2+. The data are important for understanding endogenous mechanisms regulating epileptogenesis, and for the development of novel antiepileptogenic drugs.
doi:10.1124/jpet.106.104703
PMCID: PMC1508166  PMID: 16699066
CREB- cyclic AMP-responsive element binding protein; dSP- [D-Arg1,D-Trp5,7,9,Leu11]-substance P; GalR1- galanin receptor type 1; GalR2: galanin receptor type 2; GIRK- G-protein coupled inwardly rectifying K+ channels; PTX- pertussis toxin; TPQ- tertiapin Q

Results 1-12 (12)