Characterization of the anticonvulsant activity of doxepin in various experimental seizure models in mice

In this paper, the anticonvulsant characteristics of doxepin were evaluated in numerous experimental seizure models, including maximal electroshock (MES)-, pentylenetetrazole (PTZ)-, isoniazid (ISO)-, 3-mercaptopropionic acid (3-MP)-, bicuculline (BIC)-, thiosemicarbazide (THIO)-, and strychnine (STR)-induced seizures. In addition, the acute adverse-effect profile of doxepin with respect to impairment of motor coordination was assessed with a mouse rotarod test. The evaluation of the time-course and doseresponse relationships for doxepin provided evidence that the peak maximum anticonvulsant activity and acute adverse effects occurred 5 min after intraperitoneal (ip) administration. The results also revealed that doxepin had excellent anticonvulsant activity against maximal electroshock-induced seizures in mice with a median effect value (ED₅₀) of 6.6 mg/kg. The assessment of acute adverse effects in the rotarod test revealed that doxepin induced acute neurotoxicity, and its median toxic dose (TD₅₀) was 26.4 mg/kg. Additionally, doxepin showed anticonvulsant activity in several chemically-induced seizure models, including ISO, 3-MP, BIC, and THI. Based on this study, we can conclude that the antidepressant drug doxepin may be useful for treatment of depression in patients with epilepsy due to its short time to peak maximum anticonvulsant activity after ip administration (5 min) and remarkable anticonvulsant activity (6.6 mg/kg).     

Anti-inflammatory and antinociceptive effects of 6-(4-chlorophenoxy)-tetrazolo[5,1-a]phthalazine in mice

BackgroundQUAN-0808 (6-(4-chlorophenoxy)-tetrazolo[5,1-a]phthalazine), a new phthalazine tetrazole derivative, was evaluated for the anti-inflammatory and analgesic effects.MethodsXylene-induced ear edema, carrageenan (Carr)-induced paw edema, and acetic acid-induced capillary permeability hyperactivity in mice were used to assess the anti-inflammatory effect; acetic acid-induced writhing and hot plate responses for the analgesic activity.ResultsIn the present study, QUAN-0808 (100, 200, 400 mg/kg) and indomethacin (Indo) significantly decreased xylene-induced ear edema by 33.3, 37.5, 46.6, and 45.1%, respectively, decreased Carr-induced paw edema at 1, 2, 4 h after Carr injection, and decreased the prostaglandin E2 (PGE2) and nitric oxide (NO) levels on the edema paw at 4 h after Carr injection; QUAN-0808 (100, 200, 400 mg/kg), and aspirin (Asp, 200 mg/kg) significantly decreased Evans blue exudation in acetic acid-induced capillary permeability hyperactivity model by 26.7, 28.7, 32.3 and 29.1%, respectively, and decreased the numbers of acetic acid-induced writhing response in 15 min by 40.4, 53.6, 66.4, and 64.5%, respectively. Morphine (10 mg/kg) significantly increased the latency of the hot plate response by 136.5,117.4,67.5, and 22.7%, respectively, at 30, 60, 90, 120 min after intraperitoneal injection of morphine; however, QUAN-0808 (100, 200 and 400 mg/kg) did not produce significantly antinociceptive effects in the hot plate test, suggesting that its antinociceptive action occurs via peripheral rather than a central-acting mechanism.ConclusionsThese results show that QUAN-0808 produced potential anti-inflammatory and peripheral antinociceptive effects, and indicated that the antinociceptive effects of QUAN-0808 were related to its anti-inflammatory activity in a dose-dependent manner. Therefore, as inflammation is a peripheral process, it is suggested that QUAN-0808 exerted peripheral effects. The peripheral effect mechanisms of QUAN-0808 may be related to a decrease in the production of PGE₂, NO, bradykinin and other inflammatory mediators.     

Influence of orphenadrine upon the protective activity of various antiepileptics in the maximal electroshock-induced convulsions in mice

Orphenadrine is an anticholinergic drug used in the treatment of Parkinson’s disease, and is also known to exert nonspecific antagonistic activity at the phencyclidine binding site of the N-methyl-D-aspartate (NMDA) receptor. The aim of this study was to assess the anticonvulsant properties of orphenadrine and to evaluate its effect on the anticonvulsant activity of antiepileptic drugs against maximal electroshock-induced seizures in mice. Orphenadrine given at a dose of 5.65 mg/kg elevated the electrical seizure threshold from 5.7 (5.4 – 6.1) to 6.8 (6.3–7.3) mA, while a dose of 2.8 mg/kg was ineffective. The ED₅₀ values of orphenadrine administered 10,30 and 120 min before maximal electroshock-induced convulsions were 16.8 (11.3–25.1), 17.8 (15.7–20.0) and 25.6 (23.3–28.3) mg/kg, respectively. Orphenadrine at a sub-threshold dose of 2.8 mg/kg significantly enhanced the anticonvulsant activity of valproate by reducing its ED₅₀ value from 315.8 (270.0–369.4) to 245.9 (207.1–292.0) mg/kg without affecting the free plasma levels of valproate. However, orphenadrine failed to enhance the protective activity of carbamazepine, phenytoin, phenobarbital, lamotrigine, topiramate, or oxcarbazepine against maximal electroshock-induced seizures.     

Synthesis and Anticonvulsant Activity of Ethyl 2,2‐dimethyl‐1‐(2‐substitutedhydrazinecarboxamido) Cyclopropanecarboxylate Derivatives

In this study on the development of new anticonvulsants, fourteen ethyl 2,2‐dimethyl‐1‐(2‐substitutedhydrazinecarboxamido) cyclopropanecarboxylate derivatives were synthesized and tested for anticonvulsant activity using the maximal electroshock, subcutaneous pentylenetetrazole screens, which are the most widely employed seizure models for early identification of candidate anticonvulsants. Their neurotoxicity was determined applying the rotorod test. Two compounds 6f and 6k showed promising anticonvulsant activities in both models employed for anticonvulsant evaluation. The most active compound 6k showed the maximal electroshock‐induced seizures with ED₅₀ value of 9.2 mg/kg and TD₅₀ value of 387.5 mg/kg after intraperitoneally injection to mice, which provided compound 6k with a protective index (TD₅₀/ED₅₀) of 42.1 in the maximal electroshock test.     

Influence of agmatine on the protective action of numerous antiepileptic drugs against pentetrazole-induced seizures in miceA

The aim of this study was to assess the influence of agmatine (an endogenous neuromodulator/neurotransmitter in the brain) on the protective action of numerous classical and second-generation antiepileptic drugs (clonazepam, ethosuximide, gabapentin, phenobarbital, tiagabine, vigabatrin, and valproate) in the mouse pentetrazole-induced clonic seizure model.The results indicate that agmatine (up to 100 mg/kg, ip, 45 min before the test) did not alter the threshold for pentetrazole-induced clonic seizures in mice. However, agmatine (100 mg/kg, ip) significantly attenuated the anticonvulsant effects of vigabatrin against pentetrazole-induced clonic seizures by elevating the ED₅₀ value of vigabatrin from 517.5 to 790.3 mg/kg (p < 0.01). In contrast, agmatine at a dose of 50 mg/kg did not significantly affect the anticonvulsant action of vigabatrin, although a reduction in the ED₅₀ value of the antiepileptic drug from 517.5 to 629.1 mg/kg was documented. Moreover, agmatine at doses of 50 and 100 mg/kg (ip) had no significant impact on the anticonvulsant action of clonazepam, ethosuximide, gabapentin, phenobarbital, tiagabine, or valproate in pentetrazole-induced seizures in mice.In conclusion, the combination of agmatine with vigabatrin seems to be unfavorable due to the reduction of the anticonvulsant effect of vigabatrin after concomitant administration of agmatine in the pentetrazole-induced seizure model. Therefore, the utmost caution is advised when combining agmatine with vigabatrin in further clinical settings.     

Synthesis and anticonvulsant evaluation of 3-substituted-4-(4-hexyloxyphenyl)-4H-1,2,4-triazoles

A series of 3-substituted-4-(4-hexyloxyphenyl)-4H-1,2,4-triazole derivatives (3a-s) were synthesized as open-chain analogues of 7-hexyloxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines (1c) using 4-hexyloxyaniline, acyl hydrazines, and dimethoxy-N,N-dimethylmethanamine as the starting material. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES test) and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). MES test showed that all open-chain compounds exhibited strong anticonvulsant activity and lower neurotoxicity, and that some possessed obviously stronger activity than compound 1c. Compound 3d, 3-propyl-4-(4-hexyloxyphenyl)-4H-1,2,4-triazole was found to be the most potent with an ED₅₀ value of 5.7 mg/kg and protective index (PI = TD₅₀/ED₅₀) value of 11.5, which was much greater than that of the prototype drug phenytoin (PI = 6.9).     

Structure-based design,synthesis, and anticonvulsant activity of isatin-1-N-phenylacetamide derivatives

In an effort to develop the potent anticonvulsant agents, a series of novel isatin-1-N-phenylacetamide derivatives was synthesized and screened for their in vivo anticonvulsant activity against maximal electroshock test and evaluated for their neurotoxicity by the rotarod test at the same dose levels. Ten compounds exhibited the anticonvulsant activity. 2-(5-Methyl-2,3-dioxoindolin-1-yl)-N-phenylacetamide (4b) was found to be the most potent compound of the series with an ED₅₀ of 91.3 mg/kg, TD₅₀ of >1,000 mg/kg, a higher protective index (PI = TD₅₀/ED₅₀, >11) was gained than the reference drug phenobarbital and carbamazepine. The essential structural features responsible for interaction with receptor site are established within a suggested pharmacophore.     

Effects of androsterone on convulsions in various seizure models in mice

It is believed that a deficiency of androgens, including free testosterone, may promote the development of convulsions. The present study revealed differences in the action of androsterone (AND), a major excreted metabolite of testosterone and a neurosteroid, in three commonly used seizure models in mice. AND administered intraperitoneally exhibited dose-dependent protection against tonic-clonic convulsions caused by maximal electroshock (MES) with ED₅₀ (effective dose₅₀) of 227 mg/kg. The compound also inhibited the convulsive action of pentylenetetrazole (PTZ), increasing its CD= (convulsive dose₅₀) for clonic convulsions from 77.2 (PTZ + saline) to 93.9 (p < 0.05) for PTZ +AND40 mg/kg and 113.9 mg/kg (p < 0.001) for PTZ +AND60 mg/kg. In mice pretreated with 60 mg/kg AND, the CD₅₀ for PTZ-induced tonic convulsions increased from 102 to 127.6 mg/kg (p < 0.01). Surprisingly, doses of 50 and 100 mg/kg AND lowered the CD₅₀ for kainate (KA)-induced convulsions from 40.8 to 28.7 (p < 0.05) and 25.4 mg/kg (p < 0.001), respectively. In summary, for two of the mouse seizure models, our findings confirmed previous studies that demonstrated protective activity of AND. However, the potentiation of KA-induced convulsions by AND was somewhat unexpected and suggested that AND may also possess proconvulsant activity.     

Substituted 2-[2-(pyridin-3-yl) phenyl] acetamides and ureas: design, synthesis, and anticonvulsant screening in mice

Five novel 2-[2[(pyridin-3-yl) phenyl] acetamides and ureas were designed based on a two-point pharmacophore, synthesized by improved methods, and screened for anticonvulsant activity in maximal electroshock seizure (MES) and ScPTZ-induced seizure models in Swiss mice at doses of 30, 100, and 300?mg/kg body weight. Compound 15 displayed potent anticonvulsant activity in MES test with ED₅₀ value of 8.28?mg/kg and higher protective index (TD₅₀/ED₅₀?=?26) compared with Phenytoin, which can be considered as a promising lead.     

Analgesic activity of 3-mono-substituted derivatives of dihydrofuran-2-one in experimental rodent models of pain

Three derivatives of dihydrofuran-2-one (L-PP, L-PP1, and L-SAL) were administered by intraperitoneal injection and their analgesic activity was assayed in several models of pain. The activity of these derivatives were tested using a hot plate test, a writhing test, capsaicin- and glutamate-induced nociception, along with two models of local anesthesia, including a test for infiltration anesthesia in guinea pigs and the modified tail immersion test in mice. The results of these in vivo experiments show that these three derivatives of dihydrofuran-2-one possess analgesic activity in rodents. The ED₅₀ values of the tested compounds are lower or comparable to the ED₅₀ values of reference compounds (acetylsalicylic acid or morphine). For the most active derivative of dihydrofuran-2-one, L-PP1 (3-[4-(3-trifluoromethylphenyl)-piperazin-1-yl]-dihydrofuran-2-one dihydrochloride), the ED₅₀ value was: 1.34 mg/kg, 0.79 mg/kg, 2.01 mg/kg and 3.99 mg/kg in the hot plate, writhing, capsaicin- and glutamate-induced pain tests, respectively.     

Synthesis of 6-(3-substituted-4H-1,2,4-triazol-4-yl)-2-phenylbenzo[d]oxazoles as potential anticonvulsant agents

A series of 6-(3-substituted-4H-1,2,4-triazol-4-yl)-2-phenylbenzo[d]oxazoles was synthesized. The anticonvulsant effect and neurotoxicity of the compounds were calculated with maximal electroshock (MES) test, subcutaneous pentylenetetrazole (Sc-PTZ), and rotarod tests in intraperitoneally injected mice. Among the synthesized compounds, compound 2-phenyl-6-(4H-1,2,4-triazol-4-yl)benzo[d]oxazole (3a) could be considered the potentially most useful and safe therapeutic compound, with ED₅₀ = 29.6 mg/kg, TD₅₀ = 285 mg/kg, and PI = 9.7. Its neurotoxicity was the lowest of all the synthesized compounds and was also markedly lower than that of the reference drug carbamazepine with PI value of 6.4.     

Influence of ethacrynic acid on the anticonvulsant activity of conventional antiepileptic drugs in the mouse maximal electroshock seizure model

The aim of this study was to determine whether ethacrynic acid (EA), a loop diuretic with anticonvulsant activity, would affect the protective action of the conventional antiepileptics (AEDs) carbamazepine (CBZ), phenytoin (PHT), valproate (VPA) and phenobarbital (PB) in the mouse maximal electroshock seizure (MES) model. The effects of acute and chronic treatment with EA on these AEDs were examined. At a single dose of 100 mg/kg ip, EA enhanced the antielectroshock activity of VPA, decreasing its ED₅₀ value from 225.6 to 146.6 mg/kg (p < 0.05), but enhancement was not observed following continuous administration of EA (12.5 mg/kg) for seven days. Combined treatment of EA with other AEDs had no effect on their ED₅₀ values. The observed interaction between EA and VPA was pharmacodynamic in nature as EA did not alter free plasma (non-protein-bound) and total brain concentrations of VPA. Taking into consideration the clinical use of both drugs, this interaction between EA and VPA can be important for patients receiving these drugs.     

Effects of N-(morpholinomethyl)- p-isopropoxyphenylsuccinimide on the protective action of different classical antiepileptic drugs against maximal electroshock-induced tonic seizures in mice

BackgroundThe aim of this study was to determine the effects of N-(morpholinomethyl)-p-isopropoxy-phenylsuccinimide (MMIPPS) on the protective action of four classical antiepileptic drugs (AEDs: carbamazepine [CBZ], phenobarbital [PB], phenytoin [PHT] and valproate [VPA]) against maximal electroshock (MES)-induced seizures in mice.MethodsTonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2 s stimulus duration) delivered via auricular electrodes. Total brain concentrations of AEDs were measured to determine the characteristics of interaction between MMIPPS and classical AEDs in the mouse MES model.ResultsMMIPPS administered intraperitoneally (ip) at 100 mg/kg significantly elevated the threshold for electroconvulsions in mice (p < 0.01). MMIPPS at doses of 25 and 50 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, MMIPPS (50 mg/kg) significantly enhanced the anticonvulsant activity of PB and VPA(p < 0.05), but not that of CBZ or PHT, in the MES test in mice. Pharmacokinetic studies revealed that MMIPPS (50 mg/kg) did not alter total brain concentrations of PB, but significantly elevated total brain concentrations of VPA in mice (p < 0.05).ConclusionsThe enhanced anticonvulsant action of PB byMMIPPS in themouseMESmodel and lack of any pharmacokinetic interaction between drugs make the combination of MMIPPS with PB of pivotal importance for further experimental and clinical studies. Pharmacokinetic increase in total brain VPAconcentration seems to be responsible for the enhanced anticonvulsant action of VPAby MMIPPS in the mouse MES model. The combinations of MMIPPS with CBZ and PHT are neutral from a preclinical viewpoint.     

Interactions between levetiracetam and cardiovascular drugs against electroconvulsions in mice

BackgroundHypertension and heart failure belong to common comorbid conditions with epilepsy so drug interactions between antiepileptics and cardiovascular drugs are possible in clinical practice. The aim of this study was to evaluate the effects of angiotensin AT₁ receptor antagonists (losartan potassium and candesartan cilexetil), angiotensin-converting enzyme (ACE) inhibitors (captopril and perindopril arginine) and diuretics (hydrochlorothiazide and ethacrynic acid) on the anticonvulsant activity of levetiracetam (LEV) in mice.MethodsThe protective action of LEV was examined in the maximal electroshock seizure threshold test. Drugs were administered intraperitoneally (ip). Additionally, combinations of cardiovascular drugs with LEV were tested for adverse effects in the passive avoidance task and the chimney test.ResultsLosartan potassium (50 mg/kg), candesartan cilexetil (8 mg/kg), captopril (50 mg/kg), hydrochlorothiazide (100 mg/kg) and ethacrynic acid (100 mg/kg) did not affect the anticonvulsant activity of LEV. Perindopril arginine (10 mg/kg) raised the convulsive threshold for LEV administered at doses of 100, 300 and 500 mg/kg. This interaction could be pharmacodynamic in nature because the brain concentration of LEV remained unchanged by perindopril. The adverse effects of the combined treatment with LEV and cardiovascular drugs were not observed in the passive avoidance task or the chimney test.ConclusionsAlthough experimental data can be hardly extrapolated to clinical practice, it is suggested that perindopril arginine may positively influence the anticonvulsant action of LEV in epileptic patients. The use of losartan potassium, candesartan cilexetil, captopril, hydrochlorothiazide or ethacrynic acid in patients treated with LEV seems neutral regarding its anticonvulsant activity.     

Effect of p-isopropoxyphenylsuccinimide monohydrate on the anticonvulsant action of carbamazepine,phenobarbital, phenytoin and valproate in the mouse maximal electroshock-induced seizure model

This study was designed to determine the effects of p-isopropoxyphenylsuccinimide monohydrate (IPPS) on the protective action of four classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) 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, 0.2 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 along with total brain antiepileptic drug concentrations. Results indicate that IPPS administered intraperitoneally (ip) at doses of 75 and 150 mg/kg significantly elevated the threshold for electroconvulsions in mice. IPPS at lower doses of 18.75 and 37.5 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, 37.5 mg/kg IPPS significantly enhanced the anticonvulsant activity of phenytoin and valproate, but not that of carbamazepine or phenobarbital, in the maximal electroshock seizure test in mice. IPPS (18.75 mg/kg) had no impact on the antiseizure action of phenytoin and valproate against maximal electroshock-induced seizures in mice. Pharmacokinetic experiments revealed that IPPS did not alter total brain concentrations of phenytoin or valproate in mice.In conclusion, the enhanced anticonvulsant action of phenytoin and valproate by IPPS in the mouse maximal electroshock-induced seizure model and lack of pharmacokinetic interactions make the combinations of IPPS with phenytoin and valproate of pivotal importance for further experimental and clinical studies. The combinations of IPPS with carbamazepine and phenobarbital are neutral from a preclinical viewpoint.     

Synergistic interaction of gabapentin with tiagabine in the hot-plate test in mice: an isobolographic analysis

This study was aimed at determining the analgesic effect of gabapentin and tiagabine, two antiepileptic drugs that were administered alone and in combination at a fixed ratio of 1:1, in the acute thermal pain model (hot-plate test) in mice.Linear regression analysis was used to evaluate the dose-response relationships between logarithms of antiepileptic drug doses and their resultant maximum possible antinociceptive effects in the mouse hot-plate test. From linear equations, we calculated doses that increased the antinociceptive effect by 50% (ED₅₀ values) for gabapentin, tiagabine and their combination. The type of interaction between gabapentin and tiagabine was assessed using the isobolographic analysis.Results indicated that both antiepileptic drugs produced the definite antinociceptive effect, and the experimentally derived ED₅₀ values for gabapentin and tiagabine, when applied alone, were 504.4 mg/kg and 5.67 mg/kg, respectively.With isobolography, the experimentally derived ED_{50 mix} value for the fixed ratio combination of 1:1 was 139.31 mg/kg and significantly differed from the theoretically calculated ED_{50 add} value, which was 255.04 mg/kg (p < 0.05), indicating the synergistic interaction between gabapentin and tiagabine in the hot-plate test in mice.In conclusion, the combination of tiagabine with gabapentin at a fixed ratio of 1:1 exerted a synergistic interaction in the mouse model of nociceptive pain. If the results from this study could be extrapolated to clinical settings, the combination of tiagabine with gabapentin might be beneficial for pain relief in humans.     

Synthesis and Anticonvulsant Activity of 5‐Phenyl‐[1,2,4]‐triazolo[4,3‐a]quinolines

A series of novel 5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline derivatives was synthesized by the cyclization of 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene with formohydrazide. The starting material 2‐chloro‐4‐phenyl‐1,2‐dihydronaphthalene was synthesized from ethyl‐3‐oxo‐3‐phenylpropanoate and substituted aniline. Their anticonvulsant activities were evaluated by the maximal electroshock (MES) test and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The maximal electroshock test showed that 7‐hexyloxy‐5‐phenyl‐[1,2,4]‐triazolo[4,3‐a]quinoline 4f was found to be the most potent compound with an ED₅₀ value of 6.5 mg/kg and a protective index (PI = ED₅₀ / TD₅₀) value of 35.1, which was much higher than the PI of the reference drug phenytoin.     

Synthesis and potential anticonvulsant activity of new aryl sulfonyl semicarbazide derivatives

In the present study on the development of new anticonvulsants, twelve new aryl sulfonyl semicarbazide derivatives were synthesized and tested for anticonvulsant activity using maximal electroshock (MES), subcutaneous pentylenetetrazole screens. Their neurotoxicity was determined by the rotorod test. The most active compound 5i showed the MES-induced seizures with ED₅₀ value of 7.3 mg/kg and TD₅₀ value of 402.3 mg/kg after intraperitoneally injection to mice, which provided compound 5i with a protective index (TD₅₀/ED₅₀) of 55.1 in the MES test.     

Synthesis and pharmacological properties of new GABA uptake inhibitors

Backgroundγ-Aminobutanoic acid (GABA) is the principal inhibitory neurotransmitter in the mammalian central nervous system. The identification and subsequent development of the GABA transport inhibitors which enhance the GABA-ergic transmission has shown the important role that GABA transporters play in the control of numerous functions of the nervous system. Compounds which inhibit GABA uptake are used as antiepileptic drugs (tiagabine - a selective GAT1 inhibitor), they are also being investigated for other indications, including treatment of psychosis, general anxiety, sleep disorders, drug addiction or acute and chronic pain.MethodsIn this paper, the synthesis of 2-substituted-4-(1,3-dioxoisoindolin-2-ylo)-butanamides and 2-substituted-4-amino-butanoic acids derivatives is described. These compounds were tested in vitro for their ability to inhibit GABA uptake. The inhibitory potency towards murine plasma membrane GABA transporters (mGAT1-4) was performed as [³H]GABA uptake assay based on stably transfected HEK cells. Compound 18, which demonstrated the highest affinity for mGAT1-4 (pIC50 ranged from 4.42 for mGAT1 to 5.07 for mGAT3), was additionally investigated in several behavioral tests in mice.ResultsCompound 18 increased the locomotor activity (14–38%) and had anxiolytic-like properties in the four-plate test (ED₅₀ = 9.3 mg/kg). It did not show analgesic activity in acute pain model, namely the hot plate test, however, it was antinociceptive in the acetic acid-induced writhing test (ED₅₀ = 15.3 mg/kg) and in the formalin model of tonic pain. In the latter assay, it diminished nocifensive behavior in both phases and in the first (neurogenic) phase of this test the obtained ED50 value (5.3 mg/kg) was similar to morphine (3.0 mg/kg).ConclusionCompound 18 exhibited significant anxiolytic-like properties and was antinociceptive in some models of pain in mice. Moreover, it did not impair animals' motor coordination in the chimney test. Some of the described pharmacological activities of compound 18 can be partly explained based on its affinity for plasma membrane GABA transporters.     

Effect of caffeine on the anticonvulsant effects of oxcarbazepine,lamotrigine and tiagabine in a mouse model of generalized tonic-clonic seizures

Caffeine has been reported to be proconvulsant and to reduce the anticonvulsant efficacy of a variety of antiepileptic drugs (carbamazepine, phenobarbital, phenytoin, valproate and topiramate) in animal models of epilepsy and to increase seizure frequency in patients with epilepsy. Using the mouse maximal electroshock model, the present study was undertaken so as to ascertain whether caffeine affects the anticonvulsant efficacy of the new antiepileptic drugs lamotrigine, oxcarbazepine and tiagabine. The results indicate that neither acute nor chronic caffeine administration (up to 46.2 mg/kg) affected the ED₅₀ values of oxcarbazepine or lamotrigine against maximal electroshock. Similarly, caffeine did not modify the tiagabine electroconvulsive threshold. Furthermore, caffeine had no effect on oxcarbazepine, lamotrigine and tiagabine associated adverse effects such as impairment of motor coordination (measured by the chimney test) or long-term memory (measured by the passive avoidance task). Concurrent plasma concentration measurements revealed no significant effect on lamotrigine and oxcarbazepine concentrations. For tiagabine, however, chronic caffeine (4 mg/kg) administration was associated with an increase in tiagabine concentrations. In conclusion, caffeine did not impair the anticonvulsant effects of lamotrigine, oxcarbazepine, or tiagabine as assessed by electroconvulsions in mice. Also, caffeine was without effect upon the adverse potential of the studied antiepileptic drugs. Thus caffeine may not necessarily adversely affect the efficacy of all antiepileptic drugs and this is an important observation.