Trazodone reduces the anticonvulsant action of certain classical antiepileptics in the mouse maximal electroshock model

BackgroundThe aim of the study was to examine effects of an acute and chronic treatment with trazodone, a serotonin antagonist and reuptake inhibitor (SARI), on the protective activity of four classical antiepileptic drugs provided in the maximal electroshock test in mice.MethodsElectroconvulsions were produced in mice by means of an alternating current (50 Hz, 25 mA, 0.2 s) and delivered via earclip electrodes. Motor impairment in animals were assessed in the chimney test, and long-term memory deficits were quantified in the passive-avoidance task. Brain concentrations of antiepileptic drugs were analyzed by fluorescence polarization immunoassay.ResultsThe obtained results showed that a single administration of trazodone (up to 40 mg/kg) did not influence the electroconvulsive threshold. In contrast, chronic treatment with the antidepressant (40 mg/kg) significantly increased this parameter. Furthermore, both single and chronic administration of trazodone reduced the anticonvulsant effect of phenytoin and carbamazepine against the maximal electroshock. However, the antidepressant remained without effect on the anticonvulsant action of valproate and phenobarbital. Some interactions between trazodone and antiepileptic drugs may have a pharmacodynamic background. Both, acute and chronic treatment with the antidepressant diminished the brain concentration of phenytoin. Chronic trazodone lowered the brain levels of carbamazepine and phenobarbital. Moreover, acute and chronic trazodone increased the valproate concentration in the brain. As regards undesired effects, acute and chronic trazodone (40 mg/kg), alone and in combination with phenytoin, significantly impaired long-term memory in tested animals, evaluated in the passive avoidance task. Acute trazodone (40 mg/kg) alone and combined with phenytoin produced also significant motor deficits in mice, as measured in the chimney test.ConclusionThe obtained results allow to conclude that trazodone is not a good candidate for an antidepressant drug in epileptic patients.     

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.     

Enalapril enhances the anticonvulsant activity of lamotrigine in the test of maximal electroshock

BackgroundThe aim of this study was to find out whether angiotensin-converting enzyme (ACE) inhibitors, enalapril and cilazapril, affect the anticonvulsant action of some second-generation antiepileptics, lamotrigine (LTG), topiramate (TPM) and oxcarbazepine (OXC).MethodsThe effects of ACE inhibitors on antiepileptic drugs were examined in the mouse model of maximal electroshock.ResultsEnalapril (30 mg/kg ip) potentiated the anticonvulsant action of LTG, decreasing its ED50 value from 5.3 to 3.6 mg/kg (p < 0.01). The anticonvulsant activity of TPM or OXC was not modified by enalapril. Cilazapril did not affect the protective activity of the studied antiepileptics. The interaction between enalapril and LTG could be pharmacodynamic in nature because enalapril did not change plasma and total brain concentrations of LTG.ConclusionsThis study shows that there are no negative interactions between the studied antiepileptic drugs and enalapril or cilazapril. Enalapril even enhanced the anticonvulsant activity of LTG in the MES test in mice that is thought to be a predictive model of human generalized tonic-clonic seizures.     

Effect of acute and chronic tianeptine on the action of classical antiepileptics in the mouse maximal electroshock model

BackgroundThe aim of the study was to analyze the influence of acute and chronic treatment with tianeptine, an antidepressant selectively accelerating presynaptic serotonin reuptake, on the protective activity of classical antiepileptic drugs in the maximal electroshock test in mice.MethodsElectroconvulsions were produced by means of an alternating current (50 Hz, 25 mA, 0.2 s) delivered via ear-clip electrodes. Motor impairment and long-term memory deficits in animals were quantified in the chimney test and in the passive-avoidance task, respectively. Brain concentrations of antiepileptic drugs were measured by fluorescence polarization immunoassay.ResultsAcute and chronic treatment with tianeptine (25–50 mg/kg) did not affect the electroconvulsive threshold. Furthermore, tianeptine applied in both acute and chronic protocols enhanced the anticonvulsant action of valproate and carbamazepine, but not that of phenytoin. Neither acute nor chronic tianeptine changed the brain concentrations of valproate, carbamazepine or phenytoin. On the other hand, both single and chronic administration of tianeptine diminished the brain concentration of phenobarbital. In spite of this pharmacokinetic interaction, the antidepressant enhanced the antielectroshock action of phenobarbital. In terms of adverse effects, acute/chronic tianeptine (50 mg/kg) and its combinations with classic antiepileptic drugs did not impair motor performance or long-term memory in mice.ConclusionThe obtained results justify the conclusion that tianeptine may be beneficial in the treatment of depressive disorders in the course of epilepsy.     

Influence of propafenone on the anticonvulsant activity of various novel antiepileptic drugs in the mouse maximal electroshock model

Background

The main mechanism of action of propafenone (antiarrhythmic drug) involves the inhibition of the fast inward sodium current during phase 0 of the action potential. Sodium channel-blocking activity is also characteristic for some antiepileptic drugs. Therefore, it could be assumed that propafenone may also affect seizures. In the present study, we evaluated the effect of propafenone on the protective effect of oxcarbazepine, lamotrigine, topiramate and pregabalin against the maximal electroshock-induced seizures in mice.

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.     

Cytisine inhibits the anticonvulsant activity of phenytoin and lamotrigine in mice

BackgroundCytisine (CYT), the most commonly used drug for smoking cessation in Poland, was experimentally found to induce convulsions. There is a lack of studies on the influence of CYT on the anticonvulsant activity of antiepileptic drugs (AEDs).MethodsThe effects of CYT on the anticonvulsant activity of six AEDs were examined in maximal electroshock (MES)-induced seizures in mice.ResultsSingle intraperitoneal (ip) administration of CYTin a subthreshold dose of 2 mg/kg antagonized the protective activity of ip phenytoin and lamotrigine against MES-induced seizures in mice. Adose of 1 mg/kg did not reverse the protective activity of phenytoin and lamotrigine. CYT in a dose of 2 mg/kg had no effect on the anticonvulsive activity of carbamazepine, oxcarbazepine, phenobarbital, and valproate magnesium.ConclusionCYT ability to antagonize the anticonvulsive activity of phenytoin and lamotrigine can be of serious concern for epileptic smokers, who might demonstrate therapeutic failure to these drugs resulting in possible breakthrough seizure attacks.     

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

BackgroundThe 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.MethodsTonic 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.ResultsTP10 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.ConclusionThe 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.     

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.     

Effect of topiramate on hippocampus-dependent spatial memory in rats

BackgroundTopiramate, a new generation antiepileptic agent with a complex mechanism of action, has a broad pharmacological profile which includes a neuroprotective effect. It has been proven to be efficacious in treating alcohol dependence through a previously confirmed association with memory processes.MethodsTopiramate was administered in single doses of 120 and 40 mg/kg and multiple doses of 60 mg/kg for 12 days. Its influence on the spatial memory of rats was evaluated using the Morris water maze test. The time needed to localize the platform, the distance travelled and time spent in the platform zone were recorded.ResultsSingle doses of topiramate induce deterioration of spatial memory, with high doses having more pronounced and longer lasting effects. Multiple administration of a medial dose does not significantly affect the learning process.ConclusionsThe influence of topiramate on the hippocampus-related memory processes may play a key role in its “anti-alcohol” effect.     

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.     

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.     

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.     

Characterization of acute adverse-effect profiles of selected antiepileptic drugs in the grip-strength test in mice

The aim of this study was to assess the acute adverse effects (neurotoxic) of several antiepileptic drugs (clonazepam, lamotrigine, oxcarbazepine, phenytoin, phenobarbital and topiramate) by measuring skeletal muscular strength in mice using the grip-strength test. Linear regression analysis of grip-strength in relation to drug dose-response allowed us to determine D₅₀ values, the dosages of antiepileptic drugs that reduced grip-strength in mice by 50% compared to control animals. Each of the antiepileptic drugs studied reduced skeletal muscular strength in mice in a dose-dependent manner. The D₅₀ for clonazepam was 31.7 mg/kg, lamotrigine – 47.7 mg/kg, oxcarbazepine – 87.3 mg/kg, phenobarbital – 128.7 mg/kg, phenytoin – 69.7 mg/kg, and topiramate – 509.5 mg/kg. In conclusion, the grip-strength test can aid in evaluating acute adverse effects of drugs with respect to their influence on muscular strength in experimental animals.     

Interactions of MRZ 2/576 with felbamate, lamotrigine, oxcarbazepine and topiramate in the mouse maximal electroshock-induced seizure model

This study focused on the evaluation of interactions between MRZ 2/576 (8-chloro-4-hydroxy-1-oxo-1,2-dihydropyridazino(4,5-b)quinoline-5-oxide choline salt), an N-methyl-D-aspartate (NMDA) receptor antagonist acting at the NMDA receptor/glycine(B) site and four newer antiepileptic drugs (felbamate, lamotrigine, oxcarbazepine, and topiramate) in the mouse maximal electroshock seizure model. Results indicate that MRZ 2/576 administered intraperitoneally, 5 min before the test, exerted a clear-cut anticonvulsant effect in the maximal electroshock seizure test in mice and its ED(50) value was 13.71 (11.95-15.73) mg/kg. In the subthreshold method, MRZ 2/576 (administered intraperitoneally, at a subthreshold dose of 5 mg/kg) significantly enhanced the anticonvulsant action of felbamate, oxcarbazepine and topiramate, by reducing their ED(50) values from 73.0 to 53.8 mg/kg (p < 0.05) for felbamate, from 10.77 to 7.48 mg/kg (p < 0.05) for oxcarbazepine, and from 49.3 to 28.7 mg/kg (p < 0.01) for topiramate. In contrast, MRZ 2/576 (5 mg/kg, i.p.) did not significantly affect the antiseizure effects of lamotrigine in the maximal electroshock seizure test in mice. Isobolographic transformation of data revealed that MRZ 2/576 (5 mg/kg, i.p.) exerted barely additive interactions with all investigated antiepileptic drugs in the maximal electroshock seizure test. In conclusion, the isobolographic analysis revealed that MRZ 2/576 additively cooperates with newer antiepileptic drugs in terms of suppression of maximal electroshock-induced seizures in mice.     

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.     

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).     

Concomitant use of tramadol and venlafaxine – evaluation of antidepressant-like activity and other behavioral effects in rats

BackgroundThe aim of this study was to evaluate antidepressant-like effect (Porsolt test), locomotor activity and motor coordination of joint administration of tramadol (TRM) and venlafaxine (VEN) in rats.MethodsThe tests were performed on male Wistar rats after single and chronic treatment (7 and 14 days) with TRM intraperitoneally (ip) and VEN orally (po) administered once a day. The controls were given 0.5% carboxymethylcellulose (CMC) solution (0.5 ml per rat, ip and po).ResultsIt was found that combination of TRM (5 mg/kg ip) with VEN (20 mg/kg po) caused an increased antidepressant effect compared to TRM and VEN administered alone, with no effect on locomotor activity or motor coordination in rats, which may be of clinical significance.It was also observed that reduced time of active swimming of animals in Porsolt test with an increased dose (10 and 20 mg/kg) and time of administration (7 and 14 days) of TRM were correlated with a decreased locomotor activity in rats. It may indicate the development of tolerance to TRM’s antidepressant effect in rats during chronic treatment with doses higher than 5 mg/kg.ConclusionIt can be expected that combination of low doses of TRM and VEN could potentially be feasible and relatively safe in cases with acute pain with co-existing depression, however, further investigations are needed.     

Influence of acute and subchronic oral administration of dehydroepiandrosterone (DHEA) on nociceptive threshold in rats

BackgroundDehydroepiandrosterone (DHEA), a neurosteroid, is known to be the most abundant hormone in the human body. Its role in the central nervous system has not been well defined. Previous studies indicate that DHEA is synthesized in the spinal cord and plays an important role in pain modulation. In the present study, we investigated the effect of DHEA on pain threshold in rats after both acute and subchronic treatment.MethodRats were orally administered with DHEA at a dose of 10 mg/kg once daily and the pain threshold was measured with mechanical and thermal stimuli.ResultsAfter acute treatment, DHEA exhibited pronociceptive effects which lasted up to 150 min. After subchronic administration, DHEA showed an opposite effect by elevating the pain threshold.ConclusionThe results suggest that DHEA could be indicated as a drug to improve treatment of chronic pain disorders.     

Ivabradine (a hyperpolarization activated cyclic nucleotide-gated channel blocker) elevates the threshold for maximal electroshock-induced tonic seizures in mice

BackgroundThe aim of this study was to determine the effect of ivabradine (a hyperpolarization activated cyclic nucleotide-gated channel (HCN) blocker) on the threshold for maximal electroshock (MEST)-induced tonic seizures in mice.MethodsElectroconvulsionswere produced inmice bymeans of a current (sine-wave, 50Hz,maximum500V, strength from3–10mA, ear-clip electrodes, 0.2-s stimulus duration, tonic hindlimb extension taken as the endpoint).ResultsIvabradine administered intraperitoneally (ip), 60 min before the MEST test, at doses of 5 and 10 mg/kg, did not alter the threshold for maximal electroconvulsions in mice. In contrast, ivabradine at doses of 15 and 20 mg/kg significantly elevated the threshold for maximal electroconvulsions in mice (p < 0.05 and p < 0.001, respectively). Linear regression analysis of ivabradine doses and their corresponding threshold increases allowed determination of the threshold increasing doses by 20 and 50% (TID₂₀ and TID₅₀ values) that elevate the threshold in drug-treated animals over the threshold in control animals. The experimentally derived TID₂₀ and TID₅₀ values for ivabradine were 8.70 and 18.29 mg/kg, respectively.ConclusionsBased on this preclinical study, one can ascertain that ivabradine dose-dependently increased the threshold for MEST-induced seizures, suggesting the antiseizure activity of the compound in this seizure model in mice.