Electrophysiological Screening of Bioactives: Towards the discovery of new therapeutic agents for neuropathic pain control.

Peer reviewed: YesNRC publication: N

A novel method for inducing focal ischemia in vitro

Current in vitro models of stroke involve applying oxygen-glucose deprived (OGD) media over an entire brain slice or plate of cultured neurons. Thus, these models fail to mimic the focal nature of stroke as observed clinically and with in vivo rodent models of stroke. Our aim was to develop a novel in vitro brain slice model of stroke that would mimic focal ischemia and thus allow for the investigation of events occurring in the penumbra. This was accomplished by focally applying OGD medium to a small portion of a brain slice while bathing the remainder of the slice with normal oxygenated media. This technique produced a focal infarct on the brain slice that increased as a function of time. Electrophysiological recordings made within the flow of the OGD solution (\u201ccore\u201d) revealed that neurons rapidly depolarized (anoxic depolarization; AD) in a manner similar to that observed in other stroke models. Edaravone, a known neuroprotectant, significantly delayed this onset of AD. Electrophysiological recordings made outside the flow of the OGD solution (\u201cpenumbra\u201d) revealed that neurons within this region progressively depolarized throughout the 75 min of OGD application. Edaravone attenuated this depolarization and doubled neuronal survival. Finally, synaptic transmission in the penumbra was abolished within 50 min of focal OGD application. These results suggest that this in vitro model mimics events that occur during focal ischemia in vivo and can be used to determine the efficacy of therapeutics that target neuronal survival in the core and/or penumbra.Actuellement, les mod\ue8les in vitro d\u2019AVC consistent \ue0 appliquer un milieu d\ue9pourvu d\u2019oxyg\ue8ne et de glucose sur une tranche enti\ue8re de cerveau ou une plaque de neurones en culture. Toutefois, ces mod\ue8les ne parviennent pas \ue0 imiter la nature focale de l\u2019AVC comme on l\u2019observe sur le plan clinique et dans les mod\ue8les d\u2019AVC in vivo de rongeurs. Notre objectif \ue9tait donc de mettre au point un mod\ue8le in vitro in\ue9dit de tranche de cerveau qui imiterait l\u2019isch\ue9mie focale, permettant ainsi d\u2019\ue9tudier ce qui se produit dans la r\ue9gion de la p\ue9nombre. Pour ce faire, nous avons appliqu\ue9 localement, sur une petite portion de la tranche de cerveau, du milieu d\ue9pourvu d\u2019oxyg\ue8ne et de glucose, tandis que le reste de la tranche reposait dans un milieu oxyg\ue9n\ue9 normal. Cette technique produit un infarctus focal sur la tranche de cerveau qui s\u2019\ue9tend en fonction du temps. Des enregistrements \ue9lectrophysiologiques effectu\ue9s dans le flux de la solution d\ue9pourvue d\u2019oxyg\ue8ne et de glucose (centre de l\u2019aire infarcie) ont r\ue9v\ue9l\ue9 que les neurones se d\ue9polarisent rapidement (d\ue9polarisation anoxique), de fa\ue7on similaire \ue0 d\u2019autres mod\ue8les d\u2019AVC. L\u2019\ue9daravone, un agent neuroprotecteur connu, a retard\ue9 de mani\ue8re importante l\u2019apparition de cette d\ue9polarisation anoxique. Les enregistrements \ue9lectrophysiologiques effectu\ue9s hors du flux de solution d\ue9pourvue d\u2019oxyg\ue8ne et de glucose (p\ue9nombre) ont r\ue9v\ue9l\ue9 que les neurones de cette r\ue9gion se d\ue9polarisent progressivement au cours des 75 minutes d\u2019application du milieu d\ue9pourvu d\u2019oxyg\ue8ne et de glucose. L\u2019\ue9daravone a att\ue9nu\ue9 cette d\ue9polarisation et a am\ue9lior\ue9 du double la survie des neurones. Enfin, la transmission synaptique dans la p\ue9nombre a disparu dans les 50 minutes qui ont suivi l\u2019application locale du milieu d\ue9pourvu d\u2019oxyg\ue8ne et de glucose. D\u2019apr\ue8s les r\ue9sultats obtenus, ce mod\ue8le in vitro imite ce qui se produit au cours d\u2019une isch\ue9mie focale in vivo et il est possible de l\u2019utiliser pour v\ue9rifier l\u2019efficacit\ue9 de traitements qui visent la survie des neurones dans le centre et la p\ue9nombre d\u2019une aire infarcie.Peer reviewed: YesNRC publication: Ye

Ethyl-eicosapentaenoate modulates changes in neurochemistry and brain lipids induced by parkinsonian neurotoxin 1-methyl-4-phenylpyridinium in mouse brain slices

Evidence suggests a link between Parkinson's disease and the dietary intake of omega (n) 123 and n 126 polyunsaturated fatty acids (PUFAs). Presently, we investigated whether an acute dose of parkinsonian neurotoxin 1-methyl-4-phenylpyridinium (MPP+) affects brain n 123 and n 126 PUFA content and expression of fatty acid metabolic enzymes cytosolic phospholipase A2 (cPLA2) and cyclooxygenase-2 (COX-2) in brain slices from C57Bl/6mice. Furthermore, we investigated whether feeding a diet of n 123 PUFA ethyl-eicosapentaenoate (E-EPA) to these mice can attenuate the MPP+ induced changes in brain PUFA content and expression of cPLA2 and COX-2, and attenuate MPP+ induced changes in neurotransmitters and metabolites and apoptotic markers, bax, bcl-2 and caspase-3. MPP+ increased brain content of n 126 PUFAs linoleic acid and arachidonic acid, and increased the mRNA expression of cPLA2. MPP+ also depleted striatal dopamine levels and increased dopamine turnover, and depleted noradrenaline levels in the frontal cortex. The neurotoxin induced increases in bax, bcl-2 and caspase-3 mRNA expression that approached significance. E-EPA by itself increased brain n 123 content, including EPA and docosapentaenoic acid (C22:5, n 123), and increased cortical dopamine. More importantly, E-EPA attenuated the MPP+ induced increase in n 126 fatty acids content, partially attenuated the striatal dopaminergic turnover, and prevented the increases of pro-apoptotic bax and caspase-3 mRNAs. In conclusion, increases in n 126 PUFAs in the acute stage of exposure to parkinsonian neurotoxins may promote pro-inflammatory conditions. EPA may provide modest beneficial effects in Parkinson's disease, but further investigation is warranted.Peer reviewed: YesNRC publication: Ye

Neuropeptide Y and Epilepsy

It is a central tenet of the epilepsy field that seizures result from the imbalance of excitation over inhibition 1. The bulk of excitation is mediated by the neurotransmitter glutamate, whereas inhibition results mainly from the actions of γ-aminobutyric acid (GABA). In the neocortex and hippocampus, the intrinsic sources of GABA are the interneurons, which lately have come under intense scrutiny. It has become clear that a large number of distinct types of interneurons can be differentiated in part by the array of neuropeptides they coexpress (cf. 2). Evidence is emerging that the neuropeptide complement of interneurons plays important roles in the way that interneurons regulate excitability. Here we discuss what is known about the relation of one well-characterized neuropeptide, neuropeptide Y (NPY), and epilepsy in experimental animals and humans, and suggest possible roles for the receptors as targets for the control of excessive excitation in epilepsy