Katarzyna Socała

Acute anticonvulsant effects of capric acid in seizure tests in mice

Capric acid (CA10) is a 10-carbon medium-chain fatty acid abundant in the medium-chain triglyceride ketogenic diet (MCT KD). The purpose of this study was to characterize acute anticonvulsant effects of CA10 across several seizure tests in mice. Anticonvulsant effects of orally (p.o.) administered CA10 were assessed in the maximal electroshock seizure threshold (MEST), 6-Hz seizure threshold, and intravenous pentylenetetrazole (i.v. PTZ) seizure tests in mice. Acute effects of CA10 on motor coordination were assessed in the grip and chimney tests. Plasma and brain concentrations of CA10 were measured. Co-administration studies with CA10 and another abundant medium-chain fatty acid, caprylic acid (CA8) were performed. CA10 showed significant and dose-dependent anticonvulsant properties by increasing seizure thresholds in the 6-Hz and MEST seizure tests; it was ineffective in the i.v. PTZ seizure test. At higher doses than those effective in the 6-Hz and MEST seizure tests, CA10 impaired motor performance in the grip and chimney tests. An enhanced anticonvulsant response in the 6-Hz seizure test was produced when CA8 and CA10 were co-administered. An acute p.o. administration of CA10 resulted in dose-proportional increases in its plasma and brain concentrations. CA10 exerted acute anticonvulsant effects at doses that produce plasma exposures comparable to those reported in epileptic patients on the MCT KD. An enhanced anticonvulsant effect is observed when CA10 and the other main constituent of the MCT KD, CA8, were co-administered. Thus, acute anticonvulsant properties of CA10 and CA8 may influence the overall clinical efficacy of the MCT KD.

Effects of sarcosine, a glycine transporter type 1 inhibitor, in two mouse seizure models.

Sarcosine, a natural amino acid found in muscles and other body tissues, is an endogenous glycine transporter type 1 inhibitor that increases the glycine concentration, resulting in an indirect potentiation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. Sarcosine, similar to other NMDA receptor-activating agents, is an effective adjuvant in the treatment of schizophrenia. It is widely accepted that increased glutamatergic neurotransmission is involved in the initiation and propagation of seizures. Because sarcosine facilitates NMDA receptor function, it may affect the seizure threshold. Therefore, we examined the effects of sarcosine on the seizure threshold in two different mouse seizure models: the timed intravenous (iv) pentylenetetrazole (PTZ) infusion test and the maximal electroshock seizure threshold test. In the iv PTZ test, sarcosine did not exert a significant effect on the seizure threshold at any of the doses tested (100, 200, 400 and 800 mg/kg, ip). However, at doses of 400 and 800 mg/kg, sarcosine significantly raised the threshold for electroconvulsions (p < 0.01). The present findings indicate that sarcosine did not lower the seizure threshold. Conversely, sarcosine showed weak anticonvulsant properties by increasing the threshold current for the induction of tonic seizures. Therefore, sarcosine may be considered as a safe adjuvant treatment for schizophrenia without proconvulsant risk. In addition, the compound may serve as an interesting addition to epilepsy treatment.

Effects of sildenafil on pentylenetetrazol-induced convulsions in mice and amygdala-kindled seizures in rats

Sildenafil is the first marketed phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction and recently, for pulmonary hypertension. While the treatment was found to be highly effective, several adverse effects are associated with this compound. Among numerous central nervous system-related untoward effects, proconvulsant activity was reported. The purpose of this study was to assess the effect of sildenafil on seizure threshold in rodents. Two seizure models/tests were used: the timed intravenous (iv) pentylenetetrazol (PTZ) infusion test in mice and the amygdala-kindling model in rats. Sildenafil was administered intraperitoneally 30 min before induction of seizures. In the iv PTZ paradigm, the first myoclonic twitch, generalized clonus with loss of the righting reflex, and forelimb tonus were recorded. In the amygdala-kindling model in rats, the following parameters were analyzed: threshold for induction of epileptiform discharges in the stimulated amygdala (afterdischarge threshold, ADT), seizure severity, seizure duration, and afterdischarge duration. Sildenafil (dosage range of 5-40 mg/kg) did not significantly affect the threshold for myoclonic twitches in the timed iv PTZ infusion test in mice but significantly decreased the threshold for clonic seizures at a dose of 20 mg/kg. Sildenafil at all doses tested neither significantly influenced the focal seizure threshold in the amygdala-kindling model of epilepsy in rats nor influenced seizure severity. Sildenafil significantly shortened afterdischarge duration and seizure duration recorded at the ADT current, indicative of a weak anticonvulsant activity. Our results show that sildenafil may have both pro- and anticonvulsant activity, which depends on the experimental model of epilepsy, on animal species and the dose of sildenafil. Based on these data and in view of the clinical observations, sildenafil should be used in patients suffering from epilepsy with caution and only based on a careful individual risk/benefit evaluation.

Effect of quercetin and rutin in some acute seizure models in mice

Quercetin is one of the most widely occurring flavonoid which is also often present in plants as glycosidic form - rutin. These compounds are ingredients of plant diet and are also present in numerous pharmaceutical preparations and diet supplements which are taken by patients suffering from epilepsy and treating with antiepileptic drugs (AEDs). Influence of these compounds on central nervous system-related effects was proved both in experimental and clinical studies. Their influence on anxiety, depression, memory processes and convulsant activity was reported. The aim of the present study was to investigate the effect of quercetin and rutin in some models of seizures, i.e., in the model of psychomotor seizures induced by 6Hz stimulation, in the maximal electroshock seizure threshold and intravenous pentylenetetrazole tests in mice. We also examined a possible mechanism of anticonvulsant activity of quercetin and its influence on action of two AEDs, i.e., valproic acid and levetiracetam, in the 6Hz seizure test. Our results revealed only a weak anticonvulsant potential of the studied flavonoids because they showed anticonvulsant action at doses from 10 to 200mg/kg only in the 6Hz test and did not change seizure thresholds in the remaining tests. Moreover, anticonvulsant action of the studied flavonoids was short-term, noted only at pretreatment time ranging between 30 and 60min. The highest anticonvulsant activity of quercetin was correlated with its high plasma and brain concentration, which was revealed in a pharmacokinetic study. We did not note changes in the anticonvulsant action of the used AEDs combined with quercetin in the model of psychomotor seizures in mice. Neither quercetin and rutin nor combinations of quercetin with the studied AEDs produced any significant impairments of motor coordination (assessed in the chimney test), muscular strength (investigated in the grip-strength test) and long-term memory (evaluated in the passive avoidance test) in mice. The results of the present study suggest that quercetin and rutin have only weak and short-term anticonvulsant potential. These flavonoids seem to be safe for patients with epilepsy because they neither changed activity of the studied AEDs nor produced any adverse effects.

Effect of sildenafil, a selective phosphodiesterase 5 inhibitor, on the anticonvulsant action of some antiepileptic drugs in the mouse 6-Hz psychomotor seizure model.

Sildenafil, a selective phosphodiesterase 5 inhibitor (PDE5), has been recently reported to have both pro- and anticonvulsant action in various experimental models of seizures and epilepsy. Furthermore, it affects anticonvulsant action of some antiepileptic drugs (AEDs) in mice seizure tests and both pharmacodynamic and pharmacokinetic interactions were noted. The present study was carried out to investigate influence of sildenafil on the threshold for 6 Hz-induced psychomotor seizures in mice. Effect of sildenafil on activity of some AEDs, i.e., phenobarbital (PB), clonazepam (CZP), ethosuximide (ETS), valproic acid (VPA), tiagabine (TGB), oxcarbazepine (OXC) and levetiracetam (LEV), in 6 Hz test was also examined. Moreover, combination of sildenafil with LEV was investigated in terms of influence on motor coordination (determined by the chimney test), muscular strength (evaluated in the grip-strength test) and long-term memory (assessed in the passive avoidance task) in mice. To determine the type of pharmacological interaction between sildenafil and LEV, free plasma and total brain concentrations of this AED were determined by LC-MS/MS method. Sildenafil at a dose ranging from 10 to 40 mg/kg statistically increased psychomotor seizure threshold in mice. Moreover, sildenafil enhanced the anticonvulsant action of all the studied AEDs in this test. Interactions between this PDE5 inhibitor and PB, CZP, ETS, TGB and OXC seem to be pharmacodynamic. Since sildenafil increased free plasma and total brain concentration of LEV, interactions between these drugs have pharmacokinetic nature. This kind of interaction was also noted between sildenafil and VPA. Neither LEV (2.32 mg/kg) nor its co-administration with sildenafil (40 mg/kg) produced any significant changes in motor coordination, muscular strength and long-term memory in mice.

Lack of effect of sildenafil on cocaine-induced convulsions in mice

The convulsant action of cocaine and the proconvulsant effects of sildenafil, a drug which is widely used in the treatment of erectile dysfunction, have been documented both in humans and mice. Since it was reported that sildenafil alone, and in conjunction with cocaine, is used recreationally, the present study was performed to examine the influence of sildenafil on cocaine-induced seizures in mice.We showed that administration of sildenafil (5-20 mg/kg, ip) did not affect latency to clonic seizures induced by ip administration of cocaine at a dose of 85 mg/kg, nor did it influence seizure incidence and mortality.We conclude that sildenafil does not significantly increase the risk of seizures when co-administered with cocaine.

Evaluation of the antidepressant- and anxiolytic-like activity of α-spinasterol, a plant derivative with TRPV1 antagonistic effects, in mice.

The transient receptor potential vanilloid 1 (TRPV1) receptor has recently gained attention as a new molecular target in the treatment of mental disorders such as depression and anxiety. α-Spinasterol is a plant steroid that acts as a TRPV1 antagonist. The present study was undertaken to evaluate the antidepressant- and anxiolytic-like properties of α-spinasterol in mice. The obtained results showed that α-spinasterol (at doses of 1 and 2mg/kg) exerted anti-immobility effect in mice subjected to the forced swim test. Furthermore, co-administration of an ineffective dose of α-spinasterol (0.5mg/kg) with an ineffective dose of another TRPV1 antagonist - capsazepine (50 μg/mouse) produced a synergistic effect in the forced swim test. This compound was, however, devoid of anxiolytic-like effects in the elevated plus maze (at doses of 0.5-2mg/kg) and the light/dark box test (at a dose of 2mg/kg) in mice. Of note, α-spinasterol did not produce significant changes in body temperature and did not alter spontaneous locomotor activity in mice. The present study adds further support to the thesis that antagonism of the TRPV1 receptors may produce antidepressant effects. α-Spinasterol may represent a new therapeutic approach towards the development of novel antidepressant therapy. However, further detailed studies on the antidepressant potential of α-spinasterol are warranted.

Influence of sildenafil on the antidepressant activity of bupropion and venlafaxine in the forced swim test in mice

Recent studies highlight the involvement of the nitrergic system in the mechanism of action of antidepressant drugs. Sildenafil, a selective PDE5 inhibitor, was shown to abolish the anti-immobility effects of bupropion, venlafaxine and s-citalopram in mice. In this study we assessed the effects of sildenafil on the activity of bupropion and venlafaxine in the forced swim test in mice. Swim trials were conducted by placing mice in glass cylinders filled with water for 6min and the duration of the behavioral immobility during the last 4min of the test was evaluated. Locomotor activity was evaluated with photoresistor actimeters. Brain and serum concentrations of the studied antidepressants were determined by HPLC method. Sildenafil at a dose of 20mg/kg, but not 5 and 10mg/kg, significantly increased the anti-immobility action of bupropion (20mg/kg). The antidepressant activity of venlafaxine (2mg/kg) was potentiated by joint administration with sildenafil at doses of 10 and 20mg/kg. Since the combined treatments did not increase the locomotor activity, the antidepressant-like effects were not related to non-specific behavioral activation. Data from pharmacokinetic studies revealed that sildenafil increased bupropion and venlafaxine levels in serum without affecting their concentrations in the brain. The present study demonstrates the enhancement of anti-immobility action of bupropion and venlafaxine by sildenafil co-administration. The observed changes might have been partly due to pharmacokinetic interactions. However, mechanisms underlying the effects of sildenafil on the antidepressant activity of bupropion and venlafaxine should be carefully evaluated in further studies.

Sildenafil, a phosphodiesterase type 5 inhibitor, enhances the activity of two atypical antidepressant drugs, mianserin and tianeptine, in the forced swim test in mice.

Sildenafil, a selective phosphodiesterase type 5 inhibitor, has recently been reported to abolish anti-immobility action of antidepressant drugs, i.e., bupropion, venlafaxine and S-citalopram, in the forced swim test in mice. The present study was designed to investigate the influence of sildenafil on the potential of two atypical antidepressants, namely mianserin and tianeptine. Swim sessions were conducted by placing mice in glass cylinders filled with water for 6 min and the duration of the behavioral immobility during the last 4 min of the test was evaluated. Locomotor activity was measured with photoresistor actimeters. To evaluate the potential pharmocokinetic interaction, total brain concentrations of the studied antidepressants were determined by HPLC method. Sildenafil at a dose of 2.5 mg/kg did not affect the activity of mianserin (20 mg/kg) in the forced swim test. Interestingly, at higher doses (5 and 10 mg/kg), sildenafil significantly enhanced the anti-immobility action of mianserin. Likewise, sildenafil (5, 10 and 20 mg/kg) robustly augmented the antidepressant activity of tianeptine (30 mg/kg). Mianserin alone, as well as in a combination with sildenafil at the highest dose, caused a potent reduction in locomotor activity. However, the changes in motor activity did not interfere with the data obtained in the forced swim test. Sildenafil significantly increased the total brain tianeptine concentration. No alteration in mianserin level in the brain after sildenafil co-administration was observed. The present study suggests that sildenafil enhances the activity of mianserin and tianeptine in the forced swim test in mice. The changes in the antidepressant activity of mianserin evoked by sildenafil co-administration were related to pharmacodynamic interaction while the interaction between tianeptine and sildenafil was, at least in part, pharmacokinetic in nature.

Role of the adenosine system and glucose restriction in the acute anticonvulsant effect of caprylic acid in the 6 Hz psychomotor seizure test in mice.

Although several studies have reported the acute anticonvulsant activity of caprylic acid in animal seizure models, little is known about the mechanism underlying this effect. Recently, the role of adenosine in the efficacy of the ketogenic diet has been postulated. Therefore, the present study aimed to evaluate the possible involvement of the adenosine system (in non-fasted mice) as well as the role of glucose restriction (in fasted and non-fasted mice) in the acute anticonvulsant activity of caprylic acid in the 6 Hz psychomotor seizure threshold test. We showed that the anticonvulsant effect of caprylic acid (30 mmol/kg, p.o.) was reversed by a selective adenosine A1 receptor antagonist (DPCPX, 1mg/kg, i.p.) and a selective adenosine A2A receptor antagonist (KW-6002, 1 mg/kg, p.o.) but not by glibenclamide (1 pg/mouse, i.c.v.) - the ATP-sensitive potassium (KATP) channel blocker. Co-administration of an ineffective dose of caprylic acid (20 mmol/kg) with an ineffective dose of adenosine transporter inhibitor (dipyridamole, 50 mg/kg, i.p.) significantly raised the threshold for the 6 Hz-induced seizures. A high dose of glucose (2 g/kg) significantly only diminished the anticonvulsant effect of caprylic acid (30 mmol/kg) in non-fasted mice, and this was accompanied by an increase in blood glucose level and no changes in ketone body level as compared to the caprylic acid-treated group. In both fasted and non-fasted mice treated with glucose and caprylic acid, a significant decrease in trunk blood pH occurred as compared to the control group. No alternations in motor coordination or muscular strength were noted with any drug treatment, apart from the caprylic acid and glibenclamide combination, where a significant decrease in the muscle strength was observed. The present study provides a new insight into the role of the adenosine system and low glucose usage in the mechanisms underlying the anticonvulsant effects of caprylic acid in the 6 Hz seizure test.