Transcranial Focal Electrical Stimulation Modifies Biogenic Amines' Alterations Induced by 6-Hydroxydopamine in Rat Brain.

Transcranial focal stimulation (TFS) is a non-invasive neuromodulation strategy with neuroprotective effects. On the other hand, 6-hidroxidopamine (6-OHDA) induces neurodegeneration of the nigrostriatal system producing modifications in the dopaminergic, serotoninergic, and histaminergic systems. The present study was conducted to test whether repetitive application of TFS avoids the biogenic amines' changes induced by the intrastriatal injection of 6-OHDA. Experiments were designed to determine the tissue content of dopamine, serotonin, and histamine in the brain of animals injected with 6-OHDA and then receiving daily TFS for 21 days. Tissue content of biogenic amines was evaluated in the cerebral cortex, hippocampus, amygdala, and striatum, ipsi- and contralateral to the side of 6-OHDA injection. Results obtained were compared to animals with 6-OHDA, TFS alone, and a Sham group. The present study revealed that TFS did not avoid the changes in the tissue content of dopamine in striatum. However, TFS was able to avoid several of the changes induced by 6-OHDA in the tissue content of dopamine, serotonin, and histamine in the different brain areas evaluated. Interestingly, TFS alone did not induce significant changes in the different brain areas evaluated. The present study showed that repetitive TFS avoids the biogenic amines' changes induced by 6-OHDA. TFS can represent a new therapeutic strategy to avoid the neurotoxicity induced by 6-OHDA.

Differential expression of synaptic vesicle protein 2A after status epilepticus and during epilepsy in a lithium-pilocarpine model.

Synaptic vesicle protein 2A (SV2A) has become an attractive target of investigation because of its role in the pathophysiology of epilepsy; SV2A is expressed ubiquitously throughout the brain in all nerve terminals independently of their neurotransmitter content and plays an important but poorly defined role in neurotransmission. Previous studies have shown that modifications in the SV2A protein expression could be a direct consequence of disease severity. Furthermore, these SV2A modifications may depend on specific changes in the nerve tissue following the induction of epilepsy and might be present in both excitatory and inhibitory terminals. Thus, we evaluated SV2A protein expression throughout the hippocampi of lithium-pilocarpine rats after status epilepticus (SE) and during early and late epilepsy. In addition, we determined the γ-aminobutyric acid (GABA)ergic or glutamatergic nature associated with SV2A modifications. Wistar rats were treated with lithium-pilocarpine to induce SE and subsequently were shown to present spontaneous recurrent seizures (SRS). Later, we conducted an exhaustive semi-quantitative analysis of SV2A optical density (OD) throughout the hippocampus by immunohistochemistry. Levels of the SV2A protein were substantially increased in layers formed by principal neurons after SE, mainly because of GABAergic activity. No changes were observed in the early stage of epilepsy. In the late stage of epilepsy, there were minor changes in SV2A OD compared with the robust modifications of SE; however, SV2A protein expression generally showed an increment reaching significant differences in two dendritic layers and hilus, without clear modifications of GABAergic or glutamatergic systems. Our results suggest that the SV2A variations may depend on several factors, such as neuronal activity, and might appear in both excitatory and inhibitory systems depending on the epilepsy stage.

Neuroprotective effects of levetiracetam, both alone and combined with propylparaben, in the long-term consequences induced by lithium-pilocarpine status epilepticus.

Status epilepticus (SE) is a neurological condition that frequently induces severe neuronal injury in the hippocampus, subsequent epileptogenesis and pharmacoresistant spontaneous recurrent seizures (SRS). The repeated administration of LEV (a broad-spectrum antiepileptic drug) during the post-SE period does not prevent the subsequent development of SRS. However, this treatment reduces SE-induced neurodegeneration in the hippocampus. Conversely, propylparaben (PPB) is a widely used antimicrobial that blocks voltage-dependent Na+ channels, induces neuroprotection and reduces epileptiform activity in vitro. The present study attempted to determine if the neuroprotective effects induced by LEV are augmented when combined with a sub-effective dose of PPB. Long-term SE-induced consequences (hyperexcitability, high glutamate release, neuronal injury and volume loss) were evaluated in the hippocampus of rats. LEV alone, as well as combined with PPB, did not prevent the occurrence of SRS. However, animals treated with LEV plus PPB showed high prevalence of low frequency oscillations (0.1-4 Hz and 8-90 bands, p < 0.001) and low prevalence of high frequency activity (90-250 bands, p < 0.001) during the interictal period. In addition, these animals presented lower extracellular levels of glutamate, decreased rate of neurodegeneration and a similar hippocampal volume compared to the control conditions. This study's results suggest that LEV associated with PPB could represent a new therapeutic strategy to reduce long-term consequences induced by SE that facilitate pharmacoresistant SRS.

Sodium cromoglycate reduces short- and long-term consequences of status epilepticus in rats.

Several studies indicate that sodium cromoglycate (CG) induces neuroprotective effects in acute neurological conditions. The present study focused on investigating if the use of CG in rats during the post-status epilepticus (post-SE) period reduces the acute and long-term consequences of seizure activity. Our results revealed that animals that received a single dose of CG (50 mg/kg s.c.: subcutaneously) during the post-SE period showed a lower number of neurons in the process of dying in the dentate gyrus, hilus, cornu ammonis 1 (CA1), and CA3 of the dorsal hippocampus than the rats that received the vehicle. However, this effect was not evident in layers V-VI of the sensorimotor cortex or the lateral-posterior thalamic nucleus. A second experiment showed that animals that received CG subchronically (50 mg/kg s.c. every 12 h for 5 days followed by 24 mg/kg/day s.c. for 14 days using osmotic minipumps) after SE presented fewer generalized convulsive seizures and less neuronal damage in the lateral-posterior thalamic nucleus but not in the hippocampus or cortex. Our data indicate that CG can be used as a therapeutic strategy to reduce short- and long-term neuronal damage in the hippocampus and thalamus, respectively. The data also indicate that CG can reduce the expression of generalized convulsive spontaneous seizures when it is given during the latent period of epileptogenesis.

Propylparaben applied after pilocarpine-induced status epilepticus modifies hippocampal excitability and glutamate release in rats.

Propylparaben (PPB) induces cardioprotection after ischemia-reperfusion injury by inhibiting voltage-dependent Na+ channels. The present study focuses on investigating whether the i.p. application of 178mg/kg PPB after pilocarpine-induced status epilepticus (SE) reduces the acute and long-term consequences of seizure activity. Initially, we investigated the effects of a single administration of PPB after SE. Our results revealed that compared to rats receiving diazepam (DZP) plus vehicle after 2h of SE, animals receiving a single dose of PPB 1h after DZP injection presented 126% (p<0.001) lower extracellular levels of glutamate in the hippocampus. This effect was associated with an increased potency of low-frequency oscillations (0.1-13Hz bands, p<0.001), a reduced potency of 30-250Hz bands (p<0.001) and less neuronal damage in the hippocampus. The second experiment examined whether the subchronic administration of PPB during the post-SE period is able to prevent the long-term consequences of seizure activity. In comparison to animals that were treated subchronically with vehicle after SE, rats administered with PPB for 5 days presented lower hippocampal excitability and interictal glutamate release, astrogliosis, and neuroprotection in the dentate gyrus. Our data indicate that PPB, when applied after SE, can be used as a therapeutic strategy to reduce the consequences of seizure activity.

The mast cell stabilizer sodium cromoglycate reduces histamine release and status epilepticus-induced neuronal damage in the rat hippocampus.

Experiments were designed to evaluate changes in the histamine release, mast cell number and neuronal damage in hippocampus induced by status epilepticus. We also evaluated if sodium cromoglycate, a stabilizer of mast cells with a possible stabilizing effect on the membrane of neurons, was able to prevent the release of histamine, γ-aminobutyric acid (GABA) and glutamate during the status epilepticus. During microdialysis experiments, rats were treated with saline (SS-SE) or sodium cromoglycate (CG-SE) and 30 min later received the administration of pilocarpine to induce status epilepticus. Twenty-four hours after the status epilepticus, the brains were used to determine the neuronal damage and the number of mast cells in hippocampus. During the status epilepticus, SS-SE group showed an enhanced release of histamine (138.5%, p = 0.005), GABA (331 ± 91%, p ≤ 0.001) and glutamate (467%, p ≤ 0.001), even after diazepam administration. One day after the status epilepticus, SS-SE group demonstrated increased number of mast cells in Stratum pyramidale of CA1 (88%, p < 0.001) and neuronal damage in dentate gyrus, CA1 and CA3. In contrast to SS-SE group, rats from the CG-SE group showed increased latency to the establishment of the status epilepticus (p = 0.048), absence of wet-dog shakes, reduced histamine (but not GABA and glutamate) release, lower number of mast cells (p = 0.008) and reduced neuronal damage in hippocampus. Our data revealed that histamine, possibly from mast cells, is released in hippocampus during the status epilepticus. This effect may be involved in the subsequent neuronal damage and is diminished with sodium cromoglycate pretreatment.