Biology subjects

Scalmani, P.

Publications and source records attributed to Scalmani, P..

3 recordsLinked to original sources

bioRxiv2025

Bestrophin1-mediated GABA release activates large chloride currents to generate epileptiform events in the entorhinal cortex

The mechanisms that lead to the onset of a focal seizure are still not understood. We used the well-established 4-aminopyridine (4AP) ictogenesis model to analyze epileptiform discharges in the entorhinal cortex of rodents maintained in vitro. Simultaneous field potential and patch-clamp recordings demonstrated that 100 {micro}M 4AP elicited periodic and large chloride currents in both principal neurons and GABAergic interneurons that steadily matched with population spikes. These population spike-associated chloride currents (PSACCs) survived glutamate and glycine receptor blockade and were abolished by GABAA antagonists and by blocking synaptic neurotransmitters release. Antagonist of astrocyte bestrophin-1 channels inhibited PSACCs and prevented the occurrence of seizure-like events in both entorhinal cortex mouse slices and in the isolated guinea pig brain. We propose that bestrophin-1-induced GABA release likely triggered by astrocytes promotes in all neurons subtypes a large chloride current that is responsible for interictal spikes and establishes the conditions for the generation of seizure-like events.

neuroscience↗

bioRxiv2021

Rescuing epileptic and behavioral alterations in a Dravet syndrome mouse model by inhibiting eEF2K

Dravet Syndrome is a severe childhood pharmacoresistant epileptic disorder caused mainly by mutations in the SCN1A gene, which encodes for the 1 subunit of the type I voltage-gated sodium channel (NaV1.1), that cause imbalance between excitation and inhibition in the brain. We recently found that eEF2K knock out mice displayed enhanced GABAergic transmission and tonic inhibition and were less susceptible to epileptic seizures. In Scn1a+/- mice, a mouse model of the Dravet syndrome, we found that the activity of eEF2K/eEF2 pathway was enhanced. Then, we demonstrated that both genetic deletion and pharmacological inhibition of eEF2K were able to reduce the epileptic phenotype of Scn1a+/- mice. Interestingly we also found that motor coordination defect, memory impairments, and stereotyped behavior of the Scn1a+/- mice were reverted by eEF2K deletion. The analysis of spontaneous inhibitory postsynaptic currents (sIPSCs) suggested that the rescue of the pathological phenotype was driven by the potentiation of GABAergic synapses. Our data indicate that pharmacological inhibition of eEF2K could represent a novel therapeutic intervention for treating epilepsy and related comorbidities in the Dravet syndrome.

neuroscience↗

bioRxiv2020

GABAergic neurons and Nav1.1 channel hyperactivity: a novel neocortex-specific mechanism of cortical spreading depression.

Cortical spreading depression (CSD) is a pathologic mechanism of migraine. We have identified a novel neocortex-specific mechanism of CSD initiation and a novel pathological role of GABAergic neurons. Mutations of the NaV1.1 sodium channel (the SCN1A gene), which is particularly important for GABAergic neurons excitability, cause Familial Hemiplegic Migraine type-3 (FHM3), a subtype of migraine with aura. They induce gain-of-function of NaV1.1 and hyperexcitability of GABAergic interneurons in culture. However, the mechanism linking these dysfunctions to CSD and FHM3 has not been elucidated. Here, we show that NaV1.1 gain-of-function, induced by the specific activator Hm1a, or mimicked by optogenetic-induced hyperactivity of cortical GABAergic neurons, is sufficient to ignite CSD by spiking-generated extracellular K+ build-up. This mechanism is neocortex specific because, with these approaches, CSD was not generated in other brain areas. GABAergic and glutamatergic synaptic transmission is not required for optogenetic CSD initiation, but glutamatergic transmission is implicated in CSD propagation. Thus, our results reveal the key role of hyper-activation of Nav1.1 and GABAergic neurons in a novel mechanism of CSD initiation, which is relevant for FHM3 and possibly also for other types of migraine.

neuroscience↗