Isobolographic analysis of interactions between 1-methyl-1,2,3,4-tetrahydroisoquinoline and four conventional antiepileptic drugs in the mouse maximal electroshock-induced seizure model

Influence of Umbelliferone on the Anticonvulsant and Neuroprotective Activity of Selected Antiepileptic Drugs: An In Vivo and In Vitro Study

Umbelliferone (7-hydroxycoumarin; UMB) is a coumarin with many biological properties, including antiepileptic activity. This study evaluated the effect of UMB on the ability of classical and novel antiepileptic drugs (e.g., lacosamide (LCM), levetiracetam (LEV), phenobarbital (PB) and valproate (VPA)) to prevent seizures evoked by the 6-Hz corneal-stimulation-induced seizure model. The study also evaluated the influence of this coumarin on the neuroprotective properties of these drugs in two in vitro models of neurodegeneration, including trophic stress and excitotoxicity. The results indicate that UMB (100 mg/kg, i.p.) significantly enhanced the anticonvulsant action of PB (p < 0.01) and VPA (p < 0.05), but not that of LCM orLEV, in the 6-Hz test. Whether alone or in combination with other anticonvulsant drugs (at their ED50 values from the 6-Hz test), UMB (100 mg/kg) did not affect motor coordination; skeletal muscular strength and long-term memory, as determined in the chimney; grip strength; or passive avoidance tests, respectively. Pharmacokinetic characterization revealed that UMB had no impact on total brain concentrations of PB or VPA in mice. The in vitro study indicated that UMB has neuroprotective properties. Administration of UMB (1 µg/mL), together with antiepileptic drugs, mitigated their negative impact on neuronal viability. Under trophic stress (serum deprivation) conditions, UMB enhanced the neurotrophic abilities of all the drugs used. Moreover, this coumarin statistically enhanced the neuroprotective effects of PB (p < 0.05) and VPA (p < 0.001) in the excitotoxicity model of neurodegeneration. The obtained results clearly indicate a positive effect of UMB on the anticonvulsant and neuroprotective properties of the selected drugs.

Effect of Nobiletin on Experimental Model of Epilepsy

Background

The effects of nobiletin, a plant-derived flavonoid was examined against pentylenetetrazole (PTZ)-induced seizures. The study also aimed to assess whether nobiletin potentiated the effects of antiepileptic drug clonazepam (CZP).

Methods

PTZ (92 mg/kg, subcutaneous) was used to induce seizures in mice. Treatment groups (n = 18/group) received nobiletin (12.5, 25, or 50 mg/kg) via oral gavage for 6 consecutive days and 45 min prior to PTZ injection. CZP (0.015-2.0 mg/kg) was administered 15 min prior to PTZ. Skeletal muscle strength was assessed by measuring grip strength and Chimney test was performed to study the motor performance in animals. TUNEL assay was done to study neuro-apoptosis. RT-PCR and Western blot analysis were performed for assessment of mRNA and protein expressions.

Results

Nobiletin and CZP improved muscle strength and motor coordination and reduced seizure severity significantly. The administration of nobiletin and CZP, individually or in combination, downregulated seizure-induced increases in apoptotic cell count and apoptotic protein expression, modulated the expression of gamma-aminobutyric acid (GABA)A and glutamate decarboxylase 65 and restored the glutamate/GABA balance. Nobiletin and CZP administration significantly upregulated phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling.

Conclusion

Nobiletin exerted protective effect against seizures by regulating signaling pathways associated with epileptogenesis and potentiated the effects of CZP.

Influence of dronedarone (a class III antiarrhythmic drug) on the anticonvulsant potency of four classical antiepileptic drugs in the tonic-clonic seizure model in mice

Increasing evidence indicates that some antiarrhythmic drugs play a pivotal role in seizures, not only in vivo studies on animals, but also in clinical trials. Some of these antiarrhythmic drugs potentiate or alleviate the anticonvulsant action of the classical antiepileptic drugs. The aim of this study was to determine the influence of dronedarone (DRO-a multichannel blocker belonging to the class III of antiarrhythmic drugs) on the anticonvulsant effects of four standard antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) in the tonic-clonic seizure model in mice. Potential acute adverse effects exerted by the antiepileptic drugs combined with DRO were evaluated in three behavioral tests (chimney, grip-strength and passive avoidance). To confirm the nature of interaction, total brain concentrations of antiepileptic drugs were measured. DRO (50 mg/kg, i.p.) significantly reduces the anticonvulsant potency of phenytoin (P < 0.05), having no impact on that of carbamazepine, phenobarbital and valproate in the tonic-clonic seizure model in mice. DRO (50 mg/kg) neither changed total brain concentrations of phenytoin in mice, nor affected normal behavior in experimental animals subjected to the chimney, grip-strength and passive avoidance tests. In conclusion, DRO should not be combined with phenytoin because it reduced the anticonvulsant effects of the latter drug in experimental animals. The combined administration of DRO with carbamazepine, phenobarbital and valproate resulted in neutral interaction between these drugs in the tonic-clonic seizure model in mice.

Effects of arachidonyl-2'-chloroethylamide (ACEA) on the protective action of various antiepileptic drugs in the 6-Hz corneal stimulation model in mice

Accumulating evidence indicates that cannabinoid CB1 receptor ligands play a pivotal role in seizures, not only in preclinical studies on animals, but also in clinical settings. This study was aimed at characterizing the influence of arachidonyl-2'-chloroethylamide (ACEA-a selective cannabinoid CB1 receptor agonist) co-administered with phenylmethylsulfonyl fluoride (PMSF) on the anticonvulsant potency of various antiepileptic drugs (clobazam, lacosamide, levetiracetam, phenobarbital, tiagabine and valproate) in the 6-Hz corneal stimulation model. Psychomotor seizures in male albino Swiss mice were evoked by a current (32 mA, 6 Hz, 3 s stimulus duration) delivered via corneal electrodes. Potential adverse effects produced by the antiepileptic drugs in combination with ACEA+PMSF were assessed using the chimney test (motor performance), passive avoidance task (remembering and acquisition of learning), and grip-strength test (muscular strength). Brain concentrations of antiepileptic drugs were measured by HPLC to exclude any pharmacokinetic contribution to the observed effect. ACEA (5 mg/kg, i.p.) + PMSF (30 mg/kg, i.p.) significantly potentiated the anticonvulsant potency of levetiracetam (P<0.05), but not that of clobazam, lacosamide, phenobarbital, tiagabine or valproate in the 6-Hz corneal stimulation model. Moreover, ACEA+PMSF did not significantly affect total brain concentrations of levetiracetam in mice. No behavioral side effects were observed in animals receiving combinations of the studied antiepileptic drugs with ACEA+PMSF. In conclusion, the combined administration of ACEA+PMSF with levetiracetam is associated with beneficial anticonvulsant pharmacodynamic interaction in the 6-Hz corneal stimulation model. The selective activation of cannabinoid CB1 receptor-mediated neurotransmission in the brain may enhance levetiracetam-related suppression of seizures in epilepsy patients, contributing to the efficacious treatment of epilepsy in future.

Influence of MPEP (a selective mGluR5 antagonist) on the anticonvulsant action of novel antiepileptic drugs against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effects of 2-methyl-6-(phenylethynyl)pyridine (MPEP - a selective antagonist for the glutamate metabotropic receptor subtype mGluR5) on the protective action of some novel antiepileptic drugs (lamotrigine, oxcarbazepine, pregabalin and topiramate) against maximal electroshock-induced seizures in mice. Brain concentrations of antiepileptic drugs were measured to determine whether MPEP altered pharmacokinetics of antiepileptic drugs. Intraperitoneal injection of 1.5 and 2mg/kg of MPEP significantly elevated the threshold for electroconvulsions in mice, whereas MPEP at a dose of 1mg/kg considerably enhanced the anticonvulsant activity of pregabalin and topiramate, but not that of lamotrigine or oxcarbazepine in the maximal electroshock-induced seizures in mice. Pharmacokinetic results revealed that MPEP (1mg/kg) did not alter total brain concentrations of pregabalin and topiramate, and the observed effect in the mouse maximal electroshock seizure model was pharmacodynamic in nature. Collectively, our preclinical data suggest that MPEP may be a safe and beneficial adjunct to the therapeutic effects of antiepileptic drugs in human patients.

Additive interaction of levetiracetam with lamotrigine in the mouse 6 Hz psychomotor seizure model – an isobolographic analysis

The aim of this study was to characterize the anticonvulsant effects of levetiracetam (LEV) in combination with lamotrigine (LTG – a second-generation antiepileptic drug), in the mouse 6 Hz psychomotor seizure model. Limbic (psychomotor) seizure activity was evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3 s stimulus duration) delivered via ocular electrodes and isobolographic analysis for parallel dose-response relationship curves (DRRCs) was used to characterize the consequent anticonvulsant interactions between the drug combinations. Results indicated that LEV administered singly was associated with a DRRC that was parallel to that for LTG. With isobolography for parallel DRRCs, the combination of LEV with LTG at three fixed-ratios of 1:3, 1:1 and 3:1 exerted additive interaction. LEV combined with LTG exerted additive interaction in the mouse 6 Hz psychomotor seizure model.

Influence of N-(p-acetylphenyl)-p-isopropoxyphenylsuccinimide on the protective action of classical antiepileptic drugs against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effects of N-(p-acetylphenyl)-p-isopropoxyphenylsuccinimide (APIPPS) on the protective action of four classical antiepileptic drugs (AEDs: carbamazepine [CBZ], phenobarbital [PB], phenytoin [PHT] and valproate [VPA]) in the maximal electroshock (MES)-induced seizures in mice. Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (25mA, 500V, 50Hz, 0.2s stimulus duration) delivered via auricular electrodes. Total brain AED concentrations were measured with fluorescence polarization immunoassay to ascertain whether any observed effects were consequent to a pharmacodynamic and/or a pharmacokinetic interaction between APIPPS and classical AEDs. Results indicate that APIPPS administered intraperitoneally at a dose of 150 mg/kg significantly elevated the threshold for electroconvulsions in mice. APIPPS at lower doses of 25, 50 and 100 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, APIPPS at 100 mg/kg significantly enhanced the anticonvulsant activity of PB and VPA, but not that of CBZ or PHT, in the MES test in mice. APIPPS at a dose of 50 mg/kg significantly potentiated the anticonvulsant action of VPA, but not that of PB in the mouse MES model. Pharmacokinetic experiment revealed that APIPPS did not alter total brain concentrations of PB or VPA in mice. Summing up, the enhanced anticonvulsant action of PB and VPA by APIPPS in the mouse MES model and lack of pharmacokinetic interactions between drugs, make the combinations of APIPPS with PB and VPA of importance for further experimental and clinical studies. The combinations of APIPPS with CBZ and PHT are neutral from a preclinical viewpoint.

Effects of WIN 55,212-2 (a synthetic cannabinoid CB1 and CB2 receptor agonist) on the anticonvulsant activity of various novel antiepileptic drugs against 6 Hz-induced psychomotor seizures in mice

The purpose of this study was to determine the influence of WIN 55,212-2 mesylate (WIN-a non-selective cannabinoid CB1 and CB2 receptor agonist) on the anticonvulsant activity of various second- and third-generation antiepileptic drugs (i.e., gabapentin, lacosamide, levetiracetam, oxcarbazepine, pregabalin and tiagabine) in the mouse 6 Hz-induced psychomotor seizure model. Psychomotor seizures were evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3s stimulus duration) delivered via ocular electrodes. Additionally, total brain antiepileptic drug concentrations were measured. Results indicate that WIN (5 mg/kg, administered i.p.) significantly potentiated the anticonvulsant action of gabapentin (P < 0.05) and levetiracetam (P < 0.01), but not that of lacosamide, oxcarbazepine, pregabalin or tiagabine in the mouse psychomotor seizure model. Moreover, WIN (2.5 mg/kg) had no significant effect on the anticonvulsant activity of all tested antiepileptic drugs in the 6 Hz test in mice. Measurement of total brain antiepileptic drug concentrations revealed that WIN (5 mg/kg) had no impact on gabapentin or levetiracetam total brain concentrations, indicating the pharmacodynamic nature of interaction between these antiepileptic drugs in the mouse 6Hz model. In conclusion, WIN in combination with gabapentin and levetiracetam exerts beneficial anticonvulsant pharmacodynamic interactions in the mouse psychomotor seizure model.

Modafinil and its metabolites enhance the anticonvulsant action of classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

RATIONALE

Seizures occur when the excitability of brain circuits is not sufficiently restrained by inhibitory mechanisms. Although modafinil is reported to reduce GABA-activated currents and extracellular GABA levels in the brain, the drug exerts anticonvulsant effects in animal studies.

OBJECTIVES

The aim of this study was to determine the effects of modafinil and its metabolites (sulfone and carboxylic acid) on the anticonvulsant action of four classical antiepileptic drugs (AEDs)-carbamazepine (CBZ), phenobarbital (PB), phenytoin (PHT), and valproate (VPA).

METHODS

Anticonvulsant activity was assessed with the maximal electroshock seizure threshold (MEST) test and MES test in mice. Brain concentrations of AEDs were measured to ascertain any pharmacokinetic contribution to the observed anticonvulsant effects.

RESULTS

Intraperitoneal injection of 75 mg kg(-1) of modafinil or its metabolites significantly elevated the threshold for electroconvulsions in mice, whereas 50 mg kg(-1) of each compound enhanced the anticonvulsant activity of CBZ, PHT, and VPA, but not that of PB. A 25-mg kg(-1) dose of modafinil or its sulfone metabolite enhanced anticonvulsant activity of VPA. Modafinil and its metabolites (50 mg kg(-1)) did not alter total brain concentrations of PB and VPA but did elevate CBZ and PHT.

CONCLUSIONS

Enhancement of anticonvulsant actions of VPA by modafinil in the mouse MES model is a pharmacodynamic effect. Collectively, our data suggest that modafinil may be a safe and beneficial adjunct to the therapeutic effects of AEDs in human patients.

Additive interactions between 1-methyl-1,2,3,4-tetrahydroisoquinoline and clobazam in the mouse maximal electroshock-induced tonic seizure model--an isobolographic analysis for parallel dose-response relationship curves

BACKGROUND

The aim of this study was to characterize the anticonvulsant effect of 1-methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTHIQ) in combination with clobazam (CLB) in the mouse maximal electroshock-induced seizure (MES) model.

METHODS

The anticonvulsant interaction profile between 1-MeTHIQ and CLB in the mouse MES model was determined using an isobolographic analysis for parallel dose-response relationship curves.

RESULTS

Electroconvulsions were produced in albino Swiss mice by a current (sine wave, 25 mA, 500 V, 50 Hz, 0.2-second stimulus duration) delivered via auricular electrodes by a Hugo Sachs generator. There was an additive effect of the combination of 1-MeTHIQ with CLB (at the fixed ratios of 1:3, 1:1 and 3:1) in the mouse MES-induced tonic seizure model.

CONCLUSIONS

The additive interaction of the combination of 1-MeTHIQ with CLB (at fixed-ratios of 1:3, 1:1 and 3:1) in the mouse MES model seems to be pharmacodynamic in nature and worth of considering in further clinical practice.

Effects of WIN 55,212-2 (a non-selective cannabinoid CB1 and CB 2 receptor agonist) on the protective action of various classical antiepileptic drugs in the mouse 6 Hz psychomotor seizure model

The aim of this study was to characterize the influence of WIN 55,212-2 (WIN—a non-selective cannabinoid CB₁ and CB₂ receptor agonist) on the anticonvulsant effects of various classical antiepileptic drugs (clobazam, clonazepam, phenobarbital and valproate) in the mouse 6 Hz-induced psychomotor seizure model. Limbic (psychomotor) seizure activity was evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3 s stimulus duration) delivered via ocular electrodes. Drug-related adverse effects were ascertained by use of the chimney test (evaluating motor performance), step-through passive avoidance task (assessing learning) and grip-strength test (evaluating skeletal muscular strength). Total brain concentrations of antiepileptic drugs were measured by fluorescence polarization immunoassay to ascertain any pharmacokinetic contribution to the observed antiseizure effect. Results indicate that WIN (5 mg/kg, administered intraperitoneally) significantly enhanced the anticonvulsant action of clonazepam (P < 0.001), phenobarbital (P < 0.05) and valproate (P < 0.05), but not that of clobazam in the mouse 6 Hz model. Moreover, WIN (2.5 mg/kg) significantly potentiated the anticonvulsant action of clonazepam (P < 0.01), but not that of clobazam, phenobarbital or valproate in the 6 Hz test in mice. None of the investigated combinations of WIN with antiepileptic drugs was associated with any concurrent adverse effects with regard to motor performance, learning or muscular strength. Pharmacokinetic experiments revealed that WIN had no impact on total brain concentrations of antiepileptic drugs in mice. These preclinical data would suggest that WIN in combination with clonazepam, phenobarbital and valproate is associated with beneficial anticonvulsant pharmacodynamic interactions in the mouse 6 Hz-induced psychomotor seizure test.

Effect of 1-methyl-1,2,3,4-tetrahydroisoquinoline on the protective action of various antiepileptic drugs in the maximal electroshock-induced seizure model: a type II isobolographic analysis

The aim of this study was to characterize the interaction between 1-methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTHIQ-an endogenous parkinsonism-preventing substance) and various antiepileptic drugs [AEDs: clonazepam (CZP), ethosuximide (ETS), gabapentin (GBP), levetiracetam (LEV), tiagabine (TGB) and vigabatrin (VGB)] in the mouse maximal electroshock (MES)-induced seizure model. Results indicate that 1-MeTHIQ in combination with CZP (at the fixed ratios of 50:1 and 25:1), ETS (1:10) and GBP (1:1, 1:2, 1:5 and 1:10) exerted supra-additive (synergistic) interactions in the mouse MES model. In contrast, 1-MeTHIQ in combination with CZP (200:1 and 100:1), ETS (1:1, 1:2 and 1:5), LEV and VGB (1:1, 1:2, 1:5 and 1:10), and TGB (200:1, 100:1, 50:1 and 25:1) produced additive interaction in the mouse MES model. Total brain AED concentrations were unaffected by 1-MeTHIQ, and inversely, CZP, ETS and GBP had no impact on total brain concentrations of 1-MeTHIQ, indicating pharmacodynamic nature of synergistic interactions between 1-MeTHIQ and the tested AEDs in the mouse MES model. In conclusion, the supra-additive interactions of 1-MeTHIQ with CZP (at the fixed ratios of 50:1 and 25:1), ETS (1:10) and GBP (1:1, 1:2, 1:5 and 1:10) in the mouse MES model appear to be particularly favorable combinations from a clinical viewpoint. The additive combinations of 1-MeTHIQ with CZP (100:1, 50:1), ETS (1:1, 1:2 and 1:5), LEV and VGB (1:1, 1:2, 1:5, and 1:10), and TGB (200:1, 100:1, 50:1 and 25:1) seem to be neutral and worthy of consideration in further clinical practice.

Effects of WIN 55,212-2 mesylate on the anticonvulsant action of lamotrigine, oxcarbazepine, pregabalin and topiramate against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effect of WIN 55,212-2 mesylate (WIN - a non-selective cannabinoid CB1 and CB2 receptor agonist) on the protective action of four second-generation antiepileptic drugs (lamotrigine, oxcarbazepine, pregabalin and topiramate) in the mouse maximal electroshock seizure model. Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2s stimulus duration) delivered via auricular electrodes. Drug-related adverse effects were ascertained by use of the chimney test (evaluating motor performance), the step-through passive avoidance task (assessing long-term memory) and the grip-strength test (evaluating skeletal muscular strength). Total brain concentrations of antiepileptic drugs were measured by high-pressure liquid chromatography to ascertain any pharmacokinetic contribution to the observed antiseizure effect. Results indicate that WIN (5mg/kg, i.p.) significantly enhanced the anticonvulsant action of lamotrigine (P<0.05), pregabalin (P<0.001) and topiramate (P<0.05), but not that of oxcarbazepine in the maximal electroshock-induced tonic seizure test in mice. Furthermore, none of the investigated combinations of WIN with antiepileptic drugs were associated with any concurrent adverse effects with regards to motor performance, long-term memory or muscular strength. Pharmacokinetic characterization revealed that WIN had no impact on total brain concentrations of lamotrigine, oxcarbazepine, pregabalin and topiramate in mice. These preclinical data would suggest that WIN in combination with lamotrigine, pregabalin and topiramate is associated with beneficial anticonvulsant pharmacodynamic interactions in the maximal electroshock-induced tonic seizure test.

Influence of 5-(3-chlorophenyl)-4-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione on the anticonvulsant action of 4 classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

BACKGROUND

The aim of this study was to determine the effects of 5-(3-chlorophenyl)-4-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP10) on the protective action of 4 classical antiepileptic drugs - carbamazepine, phenobarbital, phenytoin and valproate - against maximal electroshock-induced seizures in mice.

METHODS

Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by an electric current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2 s stimulus duration) delivered via auricular electrodes. Acute adverse-effect profiles with respect to motor performance, long-term memory and skeletal muscular strength were measured, together with total brain antiepileptic drug concentrations.

RESULTS

TP10 administered intraperitoneally at 10 mg/kg significantly elevated the threshold for electroconvulsions in mice. TP10 at doses of 2.5 and 5 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, TP10 (5 mg/kg) significantly enhanced the anticonvulsant activity of valproate, but not that of carbamazepine, phenobarbital or phenytoin in the maximal electroshock seizure test in mice. Pharmacokinetic experiments revealed that TP10 significantly elevated total brain concentrations of valproate in mice.

CONCLUSIONS

The enhanced anticonvulsant action of valproate by TP10 in the mouse maximal electroshock-induced seizure model was associated with a pharmacokinetic increase in total brain valproate concentrations in mice. The combinations of TP10 with carbamazepine, phenobarbital and phenytoin were neutral from a preclinical viewpoint.

Synergistic interaction between total glucosides and total flavonoids on chronic constriction injury induced neuropathic pain in rats

CONTEXT

Shaoyao Gancao Decoction (SGD), a famous herbal medicine, consists of two herbs (Paeoniae Radix and Glycyrrhizae Radix) and is traditionally used for the treatment of pain.

OBJECTIVE

To investigate the synergistic potential of total glucosides of Paeoniae Radix (TGP) and total flavonoids of Glycyrrhizae Radix (TFL).

MATERIALS AND METHODS

Oral administration of TGP and TFL alone at the doses of 60,120 and 240 mg/kg or in combination were given only one time to the neuropathic pain rat induced by chronic constriction injury. Paw pressure and heat immersion tests were performed to assess degrees of mechanical allodynia and thermal hyperalgesia, respectively. Synergistic interactions between TGP and TFL were characterized using isobolographic analysis. Expressions of Sirt1 protein were detected by immunohistochemistry.

RESULTS AND DISCUSSION

On day 14 after surgery, single oral administration of TGP and TFL both produced significant anti-allodynic and anti-hyperalgesic effects in dose-dependent and time-dependent manners. The ED(50) value of TGP was 249.4 ± 10.8 mg/kg while TFL was 871.4 ± 30.5 mg/kg. Isobolographic analysis revealed that the combination of TGP with TFL at the fixed ratios of 3:1 exerted the highest sub-additive (synergistic) interaction, of which the experimental ED(50) value was 95.1 ± 9.0 mg/kg. SGD could also downregulate Sirt1 protein expression, which was 4.2-fold higher than that of model rats in dorsal root ganglion.

CONCLUSION

Analgesic effects of SGD may contribute to simultaneous inhibition of Sirt1 overexpression and could warrant further evaluation as a possible agent for the treatment of neuropathic pain.

Synergistic interaction of pregabalin with the synthetic cannabinoid WIN 55,212-2 mesylate in the hot-plate test in mice: an isobolographic analysis

BACKGROUND

The aim of the study was to determine the type of interaction between pregabalin (a 3(rd)-generation antiepileptic drug) and WIN 55,212-2 mesylate (WIN - a highly potent non-selective cannabinoid CB1 and CB2 receptor agonist) administered in combination at a fixed ratio of 1:1, in the acute thermal pain model (hot-plate test) in mice.

METHODS

Linear regression analysis was used to evaluate the dose-response relationships between logarithms of drug doses and their resultant maximum possible antinociceptive effects in the mouse hot-plate test. From linear equations, doses were calculated that increased the antinociceptive effect by 30% (ED(30) values) for pregabalin, WIN, and their combination. The type of interaction between pregabalin and WIN was assessed using the isobolographic analysis.

RESULTS

Results indicated that both compounds produced a definite antinociceptive effect, and the experimentally-derived ED(30) values for pregabalin and WIN, when applied alone, were 29.4 mg/kg and 10.5 mg/kg, respectively. With isobolography, the experimentally derived ED(30 mix) value for the fixed ratio combination of 1:1 was 5.7 mg/kg, and differed significantly from the theoretically calculated ED(30 add) value of 19.95 mg/kg (p < 0.01), indicating synergistic interaction between pregabalin and WIN in the hot-plate test in mice.

CONCLUSIONS

Isobolographic analysis demonstrated that the combination of WIN with pregabalin at a fixed ratio of 1:1 exerted synergistic interaction in the mouse model of acute thermal pain. If the results from this study could be adapted to clinical settings, the combination of WIN with pregabalin might be beneficial for pain relief in humans.

Effect of ACEA--a selective cannabinoid CB1 receptor agonist on the protective action of different antiepileptic drugs in the mouse pentylenetetrazole-induced seizure model

Endogenous cannabinoid ligands and cannabinoid CB1 receptor agonists have been shown to exert anticonvulsant effects in various experimental models of epilepsy. The purpose of this study was to determine the effects of arachidonyl-2'-chloroethylamide (ACEA-a highly selective cannabinoid CB1 receptor agonist) on the protective action of clonazepam, ethosuximide, phenobarbital, and valproate against pentylenetetrazole (PTZ)-induced clonic seizures in mice. To ascertain any pharmacokinetic contribution of ACEA to the observed interactions between tested drugs, free (non-protein bound) plasma and total brain concentrations of the antiepileptic drugs were estimated. Additionally, acute adverse-effect profiles of the combination of ACEA and different classical antiepileptic drugs (clonazepam, ethosuximide, phenobarbital and valproate) with respect to motor performance, long-term memory and skeletal muscular strength were measured. Results indicated that ACEA (10mg/kg, i.p.) co-administered with phenylmethylsulfonyl fluoride (PMSF-a substance protecting ACEA against degradation by the fatty-acid hydrolase; 30mg/kg, i.p.) significantly potentiated the anticonvulsant activity of ethosuximide, phenobarbital and valproate in the mouse PTZ-induced clonic seizure model by reducing their median effective doses (ED(50) values) from 122.8mg/kg to 71.7mg/kg (P<0.01; for ethosuximide), from 13.77mg/kg to 5.26mg/kg (P<0.05; for phenobarbital), and from 142.7mg/kg to 87.3mg/kg (P<0.05; for valproate), respectively. In contrast, ACEA (10mg/kg, i.p.) in combination with PMSF (30mg/kg, i.p.) had no impact on the protective action of clonazepam against PTZ-induced seizures in mice. However, ACEA (10mg/kg)+PMSF (30mg/kg) considerably increased free plasma and total brain concentrations of ethosuximide and valproate in mice suggesting a pharmacokinetic nature of interaction between drugs. In contrast, free plasma and total brain concentrations of clonazepam and phenobarbital remained unchanged after ACEA+PMSF administration and thus, indicating pharmacodynamic interactions. Moreover, none of the examined combinations of ACEA (10mg/kg, i.p.)+PMSF (30mg/kg, i.p.) with clonazepam, ethosuximide, phenobarbital, and valproate (at their ED(50) values from the PTZ-induced seizure test) affected motor coordination in the chimney test, long-term memory in the passive avoidance task, and muscular strength in the grip-strength test in mice, indicating no possible acute adverse effects in animals. In conclusion, pharmacodynamic enhancement of the anticonvulsant potency of phenobarbital by ACEA+PMSF is worthy of recommendation for further clinical settings. Pharmacokinetic interactions of ACEA+PMSF with ethosuximide and valproate seem to be responsible for a significant suppression of PTZ-induced seizures in mice. The combination of ACEA+PMSF with clonazepam seems to be neutral from a preclinical viewpoint.

Effect of 4-(4-bromophenyl)-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione on the anticonvulsant action of different classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

The aim of this study was to determine the effects of 4-(4-bromophenyl)-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP4-a new S-triazole derivative possessing anticonvulsant properties in preclinical studies) on the protective action of four different classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) against maximal electroshock-induced seizures in mice. Results indicate that TP4 administered intraperitoneally at doses of 75 and 100 mg/kg significantly elevated the threshold for electroconvulsions in mice. TP4 at doses of 12.5, 25, 37.5 and 50 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, TP4 (50 mg/kg) significantly enhanced the anticonvulsant activity of carbamazepine, phenobarbital and valproate, but not that of phenytoin in the maximal electroshock seizure test in mice. TP4 at 25 mg/kg significantly potentiated the anticonvulsant action of carbamazepine, but not that of phenobarbital, phenytoin and valproate in the mouse maximal electroshock-induced seizure model. Pharmacokinetic experiments revealed that TP4 significantly elevated total brain concentrations of carbamazepine and valproate, having no impact on total brain concentrations of phenobarbital in mice. In conclusion, the enhanced anticonvulsant action of phenobarbital by TP4 was probably pharmacodynamic in nature and, therefore, the combination of TP4 with phenobarbital is worthy of consideration while extrapolating the results from this study into clinical settings. The enhanced anticonvulsant action of carbamazepine and valproate by TP4 in the mouse maximal electroshock-induced seizure model was associated with pharmacokinetic increases in total brain concentrations of the antiepileptic drugs in mice. The combination of TP4 with phenytoin was neutral from a preclinical point of view.

Effects of WIN 55,212-2 mesylate (a synthetic cannabinoid) on the protective action of clonazepam, ethosuximide, phenobarbital and valproate against pentylenetetrazole-induced clonic seizures in mice

The aim of this study was to determine the effect of WIN 55,212-2 mesylate (WIN - a non-selective cannabinoid CB1 and CB2 receptor agonist) on the protective action of four classical antiepileptic drugs (AEDs: clonazepam [CZP], ethosuximide [ETS], phenobarbital [PB], and valproate [VPA]) in the mouse pentylenetetrazole (PTZ)-induced clonic seizure model. WIN (15 mg/kg, i.p.) significantly enhanced the anticonvulsant action of ETS, PB and VPA, but not that of CZP against PTZ-induced clonic seizures. The ED(50) values of ETS, PB and VPA were reduced from 148.0, 13.9 and 137.1mg/kg to 104.0, 8.3 and 85.6 mg/kg, respectively (P<0.05). WIN (5 and 10mg/kg, i.p.) had no impact on the anticonvulsant action of all studied AEDs against PTZ-induced clonic seizures. WIN (15 mg/kg, i.p.) significantly elevated total brain concentrations of ETS and VPA, but not those of CZP and PB in mice. Moreover, WIN combined with CZP, ETS, PB and VPA significantly impaired motor performance, long-term memory and muscular strength in mice subjected to the chimney, passive avoidance and grip-strength tests, respectively. Pharmacodynamic enhancement of the anticonvulsant action of PB by WIN against PTZ-induced clonic seizures is favorable from a preclinical viewpoint. Advantageous effects of WIN in combination with ETS and VPA against PTZ-induced seizures were pharmacokinetic in nature. However, WIN combined with CZP, ETS, PB and VPA impaired motor coordination and long-term memory as well as reduced skeletal muscular strength in the experimental animals.

Synthetic cannabinoid WIN 55,212-2 mesylate enhances the protective action of four classical antiepileptic drugs against maximal electroshock-induced seizures in mice

The aim of this study was to determine the effect of WIN 55,212-2 mesylate (WIN--a non-selective cannabinoid CB1 and CB2 receptor agonist) on the protective action of four classical antiepileptic drugs (carbamazepine, phenytoin, phenobarbital, and valproate) in the mouse maximal electroshock seizure (MES) model. The results indicate that WIN (10 mg/kg, i.p.) significantly enhanced the anticonvulsant action of carbamazepine, phenytoin, phenobarbital and valproate in the MES test in mice. WIN (5 mg/kg) potentiated the anticonvulsant action of carbamazepine and valproate, but not that of phenytoin or phenobarbital in the MES test in mice. However, WIN administered alone and in combination with carbamazepine, phenytoin, phenobarbital and valproate significantly reduced muscular strength in mice in the grip-strength test. In the passive avoidance task, WIN in combination with phenobarbital, phenytoin and valproate significantly impaired long-term memory in mice. In the chimney test, only the combinations of WIN with phenobarbital and valproate significantly impaired motor coordination in mice. In conclusion, WIN enhanced the anticonvulsant action of carbamazepine, phenytoin, phenobarbital and valproate in the MES test. However, the utmost caution is advised when combining WIN with classical antiepileptic drugs due to impairment of motor coordination and long-term memory and/or reduction of skeletal muscular strength that might appear during combined treatment.

Additive interactions of pregabalin with lamotrigine, oxcarbazepine and topiramate in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis for non-parallel dose-response relationship curves

The aim of this study was to characterize the anticonvulsant effects of pregabalin (PGB-a third-generation antiepileptic drug) in combination with three second-generation antiepileptic drugs (i.e., lamotrigine [LTG], oxcarbazepine [OXC] and topiramate [TPM]) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for non-parallel dose-response relationship curves (DRRCs). Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25mA, 500V, 50Hz, 0.2s stimulus duration) delivered via auricular electrodes. Potential adverse-effect profiles of interactions of PGB with LTG, OXC and TPM at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured. In the mouse MES model, PGB administered singly had its DRRC non-parallel to that for LTG, OXC and TPM. With type I isobolography for non-parallel DRRCs, the combinations of PGB with LTG, OXC and TPM at the fixed-ratio of 1:1 exerted additive interaction. In all combinations, neither motor coordination, long-term memory nor muscular strength were affected. In conclusion, the additive interactions between PGB and LTG, OXC and TPM are worthy of consideration while extrapolating the results from this study to clinical settings.

Interactions of stiripentol with clobazam and valproate in the mouse maximal electroshock-induced seizure model

The aim of this study was to characterize the anticonvulsant effects of stiripentol (STP) in combination with clobazam [CLB], and valproate [VPA]) in the mouse maximal electroshock (MES)-induced seizure model using the type I isobolographic analysis for parallel and non-parallel dose-response relationship curves (DRRCs). Potential adverse-effect profiles of interactions of STP with CLB and VPA at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain antiepileptic drug concentrations. In the mouse MES model, STP administered singly had its DRRC non-parallel to that for CLB and, simultaneously, parallel to that for VPA. With type I isobolography for parallel DRRCs, the combinations of STP with VPA at three fixed-ratios of 1:3, 1:1 and 3:1 exerted sub-additive (antagonistic) interaction. Isobolography for non-parallel DRRCs revealed that the combination of STP with CLB at the fixed-ratio of 1:1 produced additive interaction. For all combinations, neither motor coordination, long-term memory nor muscular strength was affected. Total brain antiepileptic drug concentrations revealed bi-direction changes with the most profound being an 18.6-fold increase in CLB by STP and a 2.3-fold increase in STP by VPA. In conclusion, the additive interaction between STP and CLB was associated with a concurrent pharmacokinetic interaction and these data may explain the clinical efficacy seen with this combination. In contrast, the antagonism between STP and VPA was surprising since synergism is observed clinically.

Interactions of 1-methyl-1,2,3,4-tetrahydroisoquinoline with lamotrigine, oxcarbazepine, pregabalin, and topiramate in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis

The aim of this study was to characterize the anticonvulsant effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline (MeTHIQ--an endogenous parkinsonism-preventing substance) in combination with four second-generation antiepileptic drugs (AEDs: lamotrigine [LTG], oxcarbazepine [OXC], pregabalin [PGB], and topiramate [TPM]) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for parallel and non-parallel dose-response relationship curves (DRRCs). Potential adverse-effect profiles of interactions of MeTHIQ with LTG, OXC, PGB and TPM at the fixed-ratio of 1:1 from the MES test with respect to motor performance, long-term memory and skeletal muscular strength were measured along with total brain concentrations of MeTHIQ and TPM. In the mouse MES model, MeTHIQ administered singly had its DRRC parallel to those for OXC and TPM, and simultaneously, non-parallel to those for LTG and PGB. With type I isobolography for parallel DRRCs, the combination of MeTHIQ with TPM at three fixed-ratios of 1:3, 1:1 and 3:1 exerted supra-additive (synergistic) interaction, whereas the combination of MeTHIQ with OXC at the fixed-ratios of 1:3, 1:1 and 3:1 produced additive interaction. Similarly, the type I isobolography for non-parallel DRRCs revealed that the combination of MeTHIQ with LTG and PGB at the fixed-ratio of 1:1 produced additive interaction. For all combinations, neither motor coordination, long-term memory nor muscular strength were affected. Total brain concentrations of MeTHIQ and TPM revealed no significant changes in their concentrations when the drugs were combined at the fixed-ratios of 1:3, 1:1 and 3:1. In conclusion, the synergistic interaction of MeTHIQ with TPM at the fixed-ratios of 1:3, 1:1 and 3:1 against MES-induced seizures was pharmacodynamic in nature and thus, it is worthy of consideration in further clinical settings. The combinations of MeTHIQ with LTG, OXC and PGB were neutral in the mouse MES model.

Effect of arachidonyl-2'-chloroethylamide, a selective cannabinoid CB1 receptor agonist, on the protective action of the various antiepileptic drugs in the mouse maximal electroshock-induced seizure model

The aim of this study was to determine the influence of arachidonyl-2'-chloroethylamide (ACEA - a highly selective cannabinoid type 1 [CB1] receptor agonist) on the protective action and acute adverse effects of carbamazepine, lamotrigine, oxcarbazepine, phenobarbital, phenytoin, and topiramate in the maximal electroshock seizure model and chimney test in mice. Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2s stimulus duration) delivered via auricular electrodes. Acute adverse-effect profiles of the studied antiepileptic drugs with respect to motor coordination was assessed in the chimney test. Additionally, long-term memory and skeletal muscular strength were measured along with free plasma (non-protein bound) and total brain antiepileptic drug concentrations. To inhibit the rapid metabolic degradation of ACEA by the fatty-acid amide hydrolase, phenylmethylsulfonyl fluoride (PMSF) was used at a constant ineffective dose of 30 mg/kg. Results indicate that ACEA (2.5 mg/kg, i.p.) co-administered with PMSF (30 mg/kg, i.p.), significantly enhanced the anticonvulsant activity of phenobarbital, but not that of carbamazepine, lamotrigine, oxcarbazepine, phenytoin, or topiramate in the maximal electroshock seizure test in mice. Moreover, ACEA (2.5 mg/kg) with PMSF (30 mg/kg) had no significant impact on the acute adverse effects of all examined antiepileptic drugs in the chimney test in mice. The protective index values (as quotients of the respective TD(50) and ED(50) values denoted from the chimney and maximal electroshock seizure tests, respectively) for the combinations of ACEA (2.5 mg/kg) and PMSF (30 mg/kg) with carbamazepine, oxcarbazepine, phenobarbital, and topiramate were greater than those denoted for the antiepileptic drugs administered alone. Only, the protective index values for the combination of ACEA (2.5 mg/kg) and PMSF (30 mg/kg) with lamotrigine and phenytoin were lower than those determined for the antiepileptic drugs administered alone. Pharmacokinetic experiments revealed that ACEA (2.5 mg/kg) and PMSF (30 mg/kg) affected neither free plasma (non-protein bound) nor total brain concentrations of phenobarbital in mice. Moreover, ACEA and PMSF in combination with carbamazepine, lamotrigine, oxcarbazepine, phenobarbital, phenytoin, and topiramate did not alter long-term memory or skeletal muscular strength in experimental animals. In conclusion, the enhanced anticonvulsant action of phenobarbital by ACEA and PMSF, lack of pharmacokinetic interaction and no acute adverse effects between the examined compounds, make the combination of ACEA and PMSF with phenobarbital of pivotal importance for further experimental and clinical studies. The combinations of ACEA and PMSF with carbamazepine, lamotrigine, oxcarbazepine, phenytoin, and topiramate are neutral from a preclinical viewpoint.

Interaction of pregabalin with carbamazepine in the mouse maximal electroshock-induced seizure model: a type I isobolographic analysis for non-parallel dose-response relationship curves

PURPOSE

To characterize the anticonvulsant effects of pregabalin (PGB - a third-generation antiepileptic drug) in combination with carbamazepine (CBZ - a classical antiepileptic drug) in the mouse maximal electroshock (MES)-induced seizure model by using the type I isobolographic analysis for non-parallel dose-response relationship curves (DRRCs).

MATERIAL/METHODS

Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25mA, 500V, 50Hz, 0.2s stimulus duration) delivered via auricular electrodes. Potential adverse-effect profiles of interaction of PGB with CBZ at the fixed-ratio of 1:1 in the MES test with respect to motor performance, long-term memory, skeletal muscular strength and antinociceptive activity were measured along with total brain CBZ concentrations.

RESULTS

In the mouse MES model, PGB administered singly had its DRRC non-parallel to that for CBZ. With type I isobolographic analysis for non-parallel DRRCs, the combination of PGB with CBZ at the fixed-ratio of 1:1 exerted additive interaction. In the combination, neither motor coordination, long-term memory nor muscular strength were affected. PGB administered alone and in combination with CBZ exerted antinociceptive effects, whereas CBZ administered alone produced no antinociceptive activity in mice subjected to the acute thermal pain model. Pharmacokinetic estimation of total brain antiepileptic drug concentrations revealed that PGB had no impact on total brain concentrations of CBZ in experimental animals.

CONCLUSIONS

In conclusion, the additive interaction between PGB and CBZ is worthy of consideration while extrapolating the results from this study to clinical settings.

Isobolographic characterization of interactions of levetiracetam with the various antiepileptic drugs in the mouse 6 Hz psychomotor seizure model

The aim of this study was to characterize the anticonvulsant effects of levetiracetam (LEV) in combination with the various antiepileptic drugs (clonazepam [CZP], oxcarbazepine [OXC], phenobarbital [PB], tiagabine [TGB], and valproate [VPA]), in the mouse 6 Hz psychomotor seizure model. Limbic (psychomotor) seizure activity was evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3s stimulus duration) delivered via ocular electrodes and isobolographic analysis for parallel and non-parallel dose-response effects was used to characterize the consequent anticonvulsant interactions between the various drug combinations. Potential concurrent adverse-effect profiles of interactions between LEV and CZP, OXC, PB, TGB, and VPA at the fixed-ratio of 1:1 were evaluated in the chimney (motor performance), passive avoidance (long-term memory), and grip-strength (muscular strength) tests. LEV administered singly was associated with a dose-response relationship curve (DRRC) that was parallel to that for CZP and non-parallel to that for OXC, PB, TGB and VPA. With isobolography for parallel DRRCs, the combination of LEV with CZP at three fixed-ratios of 1:3, 1:1 and 3:1 was additive in nature. With isobolography for non-parallel DRRCs the combinations of LEV with OXC, TGB and VPA at the fixed-ratio of 1:1 were also additive. In contrast, the isobolography for non-parallel DRRCs revealed that the interaction for the combination of LEV with PB at the fixed-ratio of 1:1 was supra-additive (synergistic). None of the combinations were associated with any concurrent adverse effects with regards to motor coordination, long-term memory or muscular strength. LEV is associated with favorable anticonvulsant synergism with PB and is additive with regards to CZP, OXC, TGB and VPA in the mouse 6 Hz psychomotor seizure model.