Computational study and synthesis of a new class of anticonvulsants with 6 Hz psychomotor seizure test activity: 2-(1,3-benzodioxol-5-yloxy)-N'- [substituted]-acetohydrazides

Background: About 50 million epileptic cases worldwide and 12 million in India are reported. Currently available drugs yield acceptable control of seizure in 60–70% patients and show many toxic effects. These actualities provoked the search of novel, more efficacious and safer anticonvulsants. Objective: Concatenation of 2-(1,3-benzodioxol-5-yloxy)-N'-[substituted]-acetohydrazides SA 1-10 was designed by molecular hybridization, optimized by computational study and synthesized with the objective of obtaining a prototype of potent anticonvulsant molecules especially active against partial seizures. Methods: Computational study was performed to calculate the pharmacophoric design, projection of the pharmacokinetic parameters and docking scores of the titled compounds with molecular targets of epilepsy. The anticonvulsant activity was ascertained by 6 Hz psychomotor seizure test. Minimal motor impairment showing neurotoxicity was assessed using Rotarod test. Results: Titled compounds possessed the indispensable elements of pharmacophore and displayed good binding affinity with molecular targets of epilepsy, such as GABA (A) alpha-1 & delta receptor, glutamate receptor, Na+ /H+ exchanger and GABA- aminotransferase in docking studies. The most potent compound of the concatenation was 2-(1,3-benzodioxol-5- yloxy)-N'-[4-(4-chlorophenoxy)benzylidene]-acetohydrazide SA 4, showing 100% protection at four different time points with ED50 value 146.8 mg/kg at a TPE of 1 h in mice. Conclusion: The protection shown in 6 Hz test is implicated as the compound's ability to control partial seizures. Thus, the titled compounds can be considered as potential prototype candidates for antiepileptic therapy against partial seizures.

Serotonergic mechanisms in the 6-Hz psychomotor seizures in mice

Serotonin (5-hydroxytrytamine (5-HT)) plays an important role in experimental seizures. Recently, we reported the depletion of 5-HT by parachlorophynylalanine (PCPA) in whole brain to enhance 6-Hz psychomotor seizures in mice. In the present work, we investigated the effect of 5-HT depletion in cortex and hippocampus, brain regions relevant for epilepsy, on behavioral and ultra-structural changes following 6-Hz psychomotor seizures in mice. In addition, we studied the effect of sodium valproate (SVP) on behavioral, biochemical, and ultra-structural effects induced by 6 Hz. Behavioral changes induced by 6 Hz stimulation were characterized as the increased duration of Straub’s tail, stun position, twitching of vibrissae, forelimb clonus, and increased rearing and grooming. PCPA administration further enhanced while SVP reduced these behaviors in mice. The 6-Hz psychomotor seizure induced ultra-structural changes in both cortex and hippocampus in mice treated with PCPA. Furthermore, PCPA administrations followed by 6Hz-induced seizures were accompanied by reduced hippocampal and cortical 5-HT. SVP attenuated the PCPA-induced ultra-structural changes and alterations of 5-HT content in the mouse brain. The study suggests the involvement of 5-HT in the 6 Hz psychomotor seizures and in the mechanisms of action of SVP against such seizures in mice.

Synergistic interaction of levetiracetam with gabapentin in the mouse 6 Hz psychomotor seizure model – a type II isobolographic analysis

This study was aimed at characterizing the anticonvulsant effects of levetiracetam in combination with gabapentin, in the mouse 6 Hz psychomotor seizure model. Herein, psychomotor seizures were evoked in male albino Swiss mice by a current (32 mA, 6 Hz, 3 s stimulus duration) delivered via ocular electrodes. Type II isobolographic analysis was used to characterize the anticonvulsant interactions between the drugs in combination, for fixed-ratios of 1:1, 1:2, 1:5 and 1:10. The type II isobolographic analysis revealed that the combinations of levetiracetam with gabapentin for the fixed-ratios of 1:5 and 1:10 were supra-additive (synergistic; P<0.05) in terms of seizure suppression, while the combinations for the fixed-ratios of 1:1 and 1:2 were additive in the mouse 6 Hz psychomotor seizure model. We conclude that, as the combinations of levetiracetam with gabapentin for the fixed-ratios of 1:5 and 1:10 exerted supra-additive (synergistic) interaction in the mouse 6 Hz psychomotor seizure model, this may be considered as particularly favorable combinations in further clinical practice.

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.