Synthesis and anticonvulsant activity of new 2-substituted-5- [2-(2-fluorophenoxy)phenyl]-1,3,4-oxadiazoles and 1,2,4-triazoles

A series of new 2-substituted-5-[2-(2-fluorophenoxy)phenyl]-1,3,4-oxadiazoles has been synthesized and screened for their anticonvulsant activities. Compound 3 shows considerable anticonvulsant activity both in PTZ and MES models. It seems that this effect is mediated by benzodiazepine receptors and other unknown mechanism, respectively.     

Behavioural assessments of neurotoxic effects and neurodegeneration in zebrafish

Altered neurological function will generally be behaviourally apparent. Many of the behavioural models pioneered in mammalian models are portable to zebrafish. Tests are available to capture alterations in basic motor function, changes associated with exteroceptive and interoceptive sensory cues, and alterations in learning and memory performance. Excepting some endpoints involving learning, behavioural tests can be carried out at 4 days post fertilization. Given larvae can be reared quickly and in large numbers, and that software solutions are readily available from multiple vendors to automatically test behavioural responses in 96 larvae simultaneously, zebrafish are a potent and rapid model for screening neurological impairments. Coupling current and emerging behavioural endpoints with molecular techniques will permit and accelerate the determination of the mechanisms behind neurotoxicity and degeneration, as well as provide numerous means to test remedial drugs and other therapies. The emphasis of this review is to highlight unexplored/underutilized behavioural assays for future studies. This article is part of a Special Issue entitled Zebrafish Models of Neurological Diseases.     

Dietary supplementation with acetyl-l-carnitine in seizure treatment of pentylenetetrazole kindled mice

In spite of the availability of new antiepileptic drugs a considerable number of epilepsy patients still have pharmacoresistant seizures, and thus there is a need for novel approaches. Acetyl-l-carnitine (ALCAR), which delivers acetyl units to mitochondria for acetyl-CoA production, has been shown to improve brain energy homeostasis and protects against various neurotoxic insults. To our knowledge, this is the first study of ALCAR's effect on metabolism in pentylenetetrazole (PTZ) kindled mice. ALCAR or the commonly used antiepileptic drug valproate, was added to the drinking water of mice for 25days, and animals were injected with PTZ or saline three times a week during the last 21days. In order to investigate ALCAR's effects on glucose metabolism, mice were injected with [1-(13)C]glucose 15min prior to microwave fixation. Brain extracts from cortex and the hippocampal formation (HF) were studied using (1)H and (13)C NMR spectroscopy and HPLC. PTZ kindling caused glucose hypometabolism, evidenced by a reduction in both glycolysis and TCA cycle turnover in both brain regions investigated. Glutamatergic and GABAergic neurons were affected in cortex and HF, but the amount of glutamate was only reduced in HF. Slight astrocytic involvement could be detected in the cortex. Interestingly, the dopamine content was increased in the HF. ALCAR attenuated the PTZ induced reduction in [3-(13)C]alanine and the increase in dopamine in the HF. However, TCA cycle metabolism was not different from that seen in PTZ kindled animals. In conclusion, even though ALCAR did not delay the kindling process, it did show some promising ameliorative effects, worthy of further investigation.     

Simple N,N-dimethyl phenylsulfonamides show potent anticonvulsant effect in two standard epilepsy models

Optimization of the previously reported benzothiazine analogue A led to the identification of compound 1, which showed anti-convulsant activity in two golden standard animal models of seizure, the MES and scPTZ models. Structure-activity relationship investigation of compound 1 revealed compounds 2, 6 and 19 as attractive anti-epileptic drug (AED) candidates with potent anticonvulsant effect in both the MES and scPTZ models. As these compounds are structurally different from existing AEDs, determination of their mechanism of actions could provide clues to understanding current therapy-resistant seizures. Moreover, these simple phenylsulfoneamide compounds could be good starting points for searching broad spectrum AEDs by such in vivo screening.     

Synthesis,modelling, and solvatochromic properties of a phenothiazine derivative

A new A–π–D–π–A phenothiazine derivative, 2,2′‐((10‐octyl‐10H‐phenothiazine‐3,7‐diyl)bis (ethene‐2,1‐diyl))bis(1‐ethyl‐3,3‐dimethyl‐3H‐indol‐1‐ium)iodide (PTZ‐BEI) was prepared and fully characterized using infra‐red (IR), ¹H nuclear magnetic resonance (NMR), ¹³C NMR, ultraviolet–visible light and mass spectra. Electronic spectra of PTZ‐BEI solutions in solvents with different polarities displayed absorption bands (λ_max) related to intramolecular charge transfer. In addition, the emission spectra of PTZ‐BEI solutions were strongly solvent dependent for both wavelength and intensity. Stokes’ shift ( increased with increasing solvent polarity up to 4105 cm^?1 in the most polar solvent, dimethylformamide. The linear solvation‐energy relationship was utilized to investigate solvent dependency of the Stokes’ shifts. Relative quantum yield (φ ) of PTZ‐BEI was calculated. Finally, density functional theory was employed at the B3LYP level for geometrical optimization and simulation of electron spectra for the PTZ derivative in gaseous and solvated states to explore the solvent effect.     

Epileptic seizures induce structural and functional alterations on brain tissue membranes

Epilepsy is characterized by disruption of balance between cerebral excitation and inhibition, leading to recurrent and unprovoked convulsions. Studies are still underway to understand mechanisms lying epileptic seizures with the aim of improving treatment strategies. In this context, the research on brain tissue membranes gains importance for generation of epileptic activities. In order to provide additional information for this field, we have investigated the effects of pentylenetetrazol-induced and audiogenetically susceptible epileptic seizures on structure, content and function of rat brain membrane components using Fourier transform infrared (FT-IR) spectroscopy.     

Neurohypophyseal hormones protect against pentylenetetrazole-induced seizures in zebrafish: Role of oxytocin-like and V1a-like receptor

Oxytocin (OT) and arginine-vasopressin (AVP) are involved in the physiological response to different stressors like the occurrence of seizures which is regarded as a severe stress factor. Zebrafish (Danio rerio) is recently featured as a model of epilepsy but the role of neurohypophyseal hormones on this teleost is still unknown. We attempted to determine whether non-mammalian homologues like isotocin (IT) and vasotocin (AVT) affected pentylenetetrazole (PTZ)-induced seizures in adult zebrafish in comparison with OT/AVP. The mechanism was studied using the most selective OT and AVP receptor antagonists. Zebrafish were injected i.m. with increasing doses (0.1-40ng/kg) of the neuropeptides 10min before PTZ exposure. DesGly-NH2-d(CH2)5-[D-Tyr2,Thr4]OVT (desglyDTyrOVT) for OT receptor and SR49059 for V1a subtype receptor, were injected together with each agonist 20min before PTZ exposure. All the peptides significantly decreased the number of seizures, increased the mean latency time to the first seizure and decreased lethality. This protective effect led to a dose-response curve following a U-shaped form. IT was approximately 40 times more active than OT while AVT was 20 times more potent than AVP in reducing the number of seizures. DesglyDTyrOVT was more effective in antagonizing OT/IT, while SR49059 mainly blocked AVP/AVT-induced protection against PTZ-induced seizures. The present findings provide direct evidence of an important involvement of IT/OT and AVP/AVT as anticonvulsant agents against PTZ-induced seizures with a receptor-mediated mechanism in zebrafish. These data reinforce zebrafish as an emerging experimental model to study and identify new antiepileptic drugs.     

Involvement of thyrotropin-releasing hormone (TRH) neural system of the brain in pentylenetetrazol-induced seizures

In order to study the relationship between pentylenetetrazol (PTZ)-induced seizures and the thyrotropin-releasing hormone (TRH) neural system, immunoreactive TRH (IR-TRH) and TRH receptor binding activity were determined in discrete regions of the rat brain before as well as 40 s (immediately before seizures), 150 s (during seizures) and 24 h after an intraperitoneal injection of PTZ (75 mg/kg). IR-TRH markedly increased in the septum 40 and 150 s after the injection, and also in the hippocampus and the thalamus-midbrain region 40 and 150 s after the injection, respectively. However, no significant changes were observed in the TRH receptor binding before, during or after the seizures, suggesting that the increased IR-TRH was not released into the synaptic cleft. This speculation was supported by the dose-dependent inhibition of PTZ-induced generalized seizures by the pre-treatment with TRH or its analogue DN-1417 into the cerebral ventricle.     

Distribution and biochemical effects of pentylenetetrazol in brains of swine treated with a polychlorinated biphenyl

In order to detect an effect on the CNS following treatment with polychlorinated biphenyls (PCB), pentylenetetrazol (PTZ) was administered to two groups of miniature swine. One group was a control and the other had been treated for 30 days with Aroclor 1254 (PCB) at a dose of 25 μg/kg in ground laboratory chow. No statistical difference was seen between the amount of PTZ administered or the time required to convulse for either group of animals. The total amount of PTZ found in brains of PCB-treated swine was less than from brains of control swine. Less PTZ was found in medulla and cerebellum from PCB-treated animals. The amount of PTZ found in motor cortex and in caudate nucleus from brains of PCB-treated swine was equal to the amounts found in similar structures of control brains. A 2–3-fold increase in dihydroxyphenylalanine (DOPA) levels was detected in motor cortex and medulla from PCB-treated animals, although levels of norepinephrine (NE) and gamma- aminobutyric acid (GABA) were unchanged from controls. It is concluded that PCB treatment had no effect on altering convulsive threshold of PTZ in swine, although PCB treatment does decrease the amount of PTZ in swine brains. Non-specific alterations in brain amine levels were also seen in PCB-treated swine.     

Synthesis and anticonvulsant activities of novel 2-(cyclopentylmethylene)hydrazinyl-1,3-thiazoles in mouse models of seizures

Synthesis, characterization and investigation of in vivo anticonvulsant activities of 13 novel cyclopentanecarbaldehyde-based 2,4-disubstituted 1,3-thiazoles are presented. Their structures were determined using ¹H and ¹³C NMR, FAB(+)-MS, HRMS and elemental analyses. The results of anticonvulsant screening reveal that seven intraperitoneally administered compounds: 3a, 3b, 3d, 3e, 3f, 3k and 3m containing F-, Cl-, Br-, CF₃-, CH₃- and adamantyl substituents demonstrated significant anticonvulsant activity in the pentylenetetrazole model with median effective doses (ED₅₀)?≤?20?mg/kg, respectively, which was approximately seven-fold lower than that reported for the reference drug, ethosuximide. Noteworthy, none of these compounds impaired animals’ motor skills in the rotarod test.