Characterization of Disopyramide derivative ADD424042 as a non-cardiotoxic neuronal sodium channel blocker with broad-spectrum anticonvulsant activity in rodent seizure models

Structure-activity relationship and cardiac safety of 2-aryl-2-(pyridin-2-yl)acetamides as a new class of broad-spectrum anticonvulsants derived from Disopyramide

A series of 2-aryl-2-(pyridin-2-yl)acetamides were synthesized and screened for their anticonvulsant activity in animal models of epilepsy. The compounds were broadly active in the 'classical' maximal electroshock seizure (MES) and subcutaneous Metrazol (scMET) tests as well as in the 6 Hz and kindling models of pharmacoresistant seizures. Furthermore, the compounds showed good therapeutic indices between anticonvulsant activity and motor impairment. Structure-activity relationship (SAR) trends clearly showed the highest activity resides in unsubstituted phenyl derivatives or compounds having ortho- and meta- substituents on the phenyl ring. The 2-aryl-2-(pyridin-2-yl)acetamides were derived by redesign of the cardiotoxic sodium channel blocker Disopyramide (DISO). Our results show that the compounds preserve the capability of the parent compound to inhibit voltage gated sodium currents in patch-clamp experiments; however, in contrast to DISO, a representative compound from the series 1 displays high levels of cardiac safety in a panel of in vitro and in vivo experiments.

Capsaicin inhibits sodium currents and epileptiform activity in prefrontal cortex pyramidal neurons

Capsaicin, a compound found in chili peppers, causes burning sensations by acting on the peripheral sensory system. However, it has also been reported to exert substantial effects on central neurons. The aim of this patch-clamp study was to test the antiepileptic potential of capsaicin in prefrontal cortical pyramidal neurons. Capsaicin at a concentration of 60 μM inhibited neuronal excitability. Moreover, later spikes in response to 50-s-long current steps were much smaller in amplitude in the presence of 60 μM capsaicin than in control solution. The tested compound did not influence the membrane potential. Voltage-clamp recordings showed that capsaicin markedly enhanced the use-dependent block of sodium channels (sodium currents were evoked at frequencies of 0,5 Hz and 10 Hz). The presence of the compound shifted the steady-state inactivation curve of sodium channels towards hyperpolarization, which suggests greater inactivation of sodium channels at rest in the presence of capsaicin. Moreover, capsaicin inhibited epileptiform events evoked in three different proepileptic solutions. Capsaicin abolished interictal-like events lasting less than 1 s recorded in zero magnesium solution with an increased potassium ion concentration. The drug also abolished long ictal events evoked in zero magnesium solution containing 4-AP. Moreover, ictal events recorded in zero magnesium solution containing picrotoxin were substantially shortened in the presence of capsaicin. We suggest that capsaicin exerts an antiepileptic effect. The important mechanism behind this phenomenon seems to be the inhibition of sodium channels, which is an effect of many antiepileptic drugs.

Valproic acid potently inhibits interictal-like epileptiform activity in prefrontal cortex pyramidal neurons

Valproic acid has a long-standing reputation of effectively treating the symptoms of not only epilepsy but also psychiatric conditions. In the latter, the exact mechanism by which valproate exerts its effect remains unclear. In this study, epileptiform bursts were recorded from pyramidal neurons in the prefrontal cortex (the brain region thought to be involved in psychiatric disorders) using the patch-clamp technique. An extracellular solution with no magnesium ions and elevated potassium levels that is known to induce epileptiform activity in vitro was used. Because of their short durations, the epileptiform bursts were regarded as interictal-like epileptiform activity, which is believed to be involved in cognitive impairment. Interictal discharges occur in many neuropsychiatric disorders as well as in healthy population. Epileptic activity in prefrontal cortex pyramidal neurons was potently inhibited by two therapeutic concentrations of valproic acid (20 μM and 200 μM). Moreover, valproate suppressed spontaneous excitatory postsynaptic potentials. Epileptiform bursts were fully inhibited by NMDA receptor antagonist, which suggests that epileptiform activity is driven by NMDA receptors. The inhibition of excitability in prefrontal cortex pyramidal neurons by valproate was also shown. This study shows that it is possible to evoke NMDA-dependent epileptiform activity in prefrontal cortex pyramidal neurons in vitro. We suggest that the prefrontal cortex is a good region for studying the influence of drugs on interictal epileptiform activity.

Electrocardiography in rats: a comparison to human

Electrocardiography (ECG) in rats is a widely applied experimental method in basic cardiovascular research. The technique of ECG recordings is simple; however, the interpretation of electrocardiographic parameters is challenging. This is because the analysis may be biased by experimental settings, such as the type of anesthesia, the strain or age of animals. Here, we aimed to review electrocardiographic parameters in rats, their normal range, as well as the effect of experimental settings on the parameters variation. Furthermore, differences and similarities between rat and human ECG are discussed in the context of translational cardiovascular research.