Alpha adrenergic receptors have role in the inhibitory effect of electrical low frequency stimulation on epileptiform activity in rats

Adrenergic receptor system as a pharmacological target in the treatment of epilepsy (Review)

Epilepsy is a complex and common neurological disorder characterized by spontaneous and recurrent seizures, affecting ~75 million individuals worldwide. Numerous studies have been conducted to develop new pharmacological drugs for the effective treatment of epilepsy. In recent years, numerous experimental and clinical studies have focused on the role of the adrenergic receptor (AR) system in the regulation of epileptogenesis, seizure susceptibility and convulsions. α1-ARs (α1A, α1B and α1D), α2-ARs (α2A, α2B and α2C) and β-ARs (β1, β2 and β3), known to have convulsant or anticonvulsant effects, have been isolated. Norepinephrine (NE), the key endogenous agonist of ARs, is considered to play a crucial role in the pathophysiology of epileptic seizures. However, the effects of NE on different ARs have not been fully elucidated. Although the activation of some AR subtypes produces conflicting results, the activation of α1, α2 and β receptor subtypes, in particular, produces anticonvulsant effects. The present review focuses on NE and ARs involved in epileptic seizure formation and discusses therapeutic approaches.

A Dual Effect of Dopamine on Hippocampal LTP and Cognitive Functions in Control and Kindled Mice

The impact of dopamine on synaptic plasticity and cognitive function following seizure is not well understood. Here, using optogenetics in the freely behaving animal, we examined exploratory behavior and short-term memory in control and kindled male mice during tonic stimulation of dopaminergic neurons within the ventral tegmental area (VTA). Furthermore, using field potential recording, we compared the effect of dopamine on synaptic plasticity in stratum radiatum and stratum oriens layers of both ventral and dorsal hippocampal CA1 regions, and again in both control and kindled male mice. Our results demonstrate that tonic stimulation of VTA dopaminergic neurons enhances novelty-driven exploration and short-term spatial memory in kindled mice, essentially rescuing the seizure-induced cognitive impairment. In addition, we found that dopamine has a dual effect on LTP in control versus kindled mice, such that application of dopamine prevented LTP induction in slices from control mice, but rescued LTP in slices taken from the kindled animal. Taken together, our results highlight the potential for dopaminergic modulation in improving synaptic plasticity and cognitive function following seizure.

The role of neurotransmitters in glioblastoma multiforme-associated seizures

GBM, or glioblastoma multiforme, is a brain tumor that poses a great threat to both children and adults, being the primary cause of death related to brain tumors. GBM is often associated with epilepsy, which can be debilitating. Seizures and the development of epilepsy are the primary symptoms that have a severe impact on the quality of life for GBM patients. It is increasingly apparent that the nervous system plays an essential role in the tumor microenvironment for all cancer types, including GBM. In recent years, there has been a growing understanding of how neurotransmitters control the progression of gliomas. Evidence suggests that neurotransmitters and neuromodulators found in the tumor microenvironment play crucial roles in the excitability, proliferation, quiescence, and differentiation of neurons, glial cells, and neural stem cells. The involvement of neurotransmitters appears to play a significant role in various stages of GBM. In this review, the focus is on presenting updated knowledge and emerging ideas regarding the interplay between neurotransmitters and neuromodulators, such as glutamate, GABA, norepinephrine, dopamine, serotonin, adenosine, and their relationship with GBM and the seizures induced by this condition. The review aims to explore the current understanding and provide new insights into the complex interactions between these neurotransmitters and neuromodulators in the context of GBM-related seizures.

High and Low-Frequency Stimulation Effect on Epileptiform Activity in Brain Slices

Background

Neurostimulation is one of the new therapeutic approaches in patients with drug-resistant epilepsy, and despite its high efficiency, its mechanism of action is still unclear. On the one hand, electrical stimulation in the human brain is immoral; on the other hand, the creation of the epilepsy model in laboratory animals affects the entire brain network. As a result, one of the ways to achieve the neurostimulation mechanism is to use epileptiform activity models In vitro. In vitro models, by accessing the local network from the whole brain, we can understand the mechanisms of action of neurostimulation.

Methods

A literature search using scientific databases including PubMed, Google Scholar, and Scopus, using "Neurostimulation" and "epileptiform activity" combined with "high-frequency stimulation", " low-frequency stimulation ", and "brain slices" as keywords were conducted, related concepts to the topic gathered and are used in this paper.

Results

Electrical stimulation causes neuronal depolarization and the release of GABAA, which inhibits neuronal firing. Also, electrical stimulation inhibits the nervous tissue downstream of the stimulation site by preventing the passage of nervous activity from the upstream to the downstream of the axon.

Conclusion

Neurostimulation techniques consisting of LFS and HFS have a potential role in treating epileptiform activity, with some studies having positive results. Further investigations with larger sample sizes and standardized outcome measures can be conducted to validate the results of previous studies.

Tonic and phasic stimulations of ventral tegmental area have opposite effects on pentylenetetrazol kindled seizures in mice

Dopamine may be involved in the anticonvulsant action of deep brain stimulation (DBS). Therefore, ventral tegmental area (VTA), as a brain dopaminergic nucleus, may be a suitable target for DBS anticonvulsant action. This study investigated the effect of tonic and phasic stimulations of the VTA on seizure parameters. Seizures were induced in adult mice by sequential injections of a sub-convulsive dose of 35 mg/kg pentylenetetrazole (PTZ) every 48 h to develop the chemical kindling until the mice reached full kindled state (showing three consecutive seizure stages 4 or 5). Fully kindled mice received DBS once a day as tonic (square waves at 1 Hz; pulse duration: 200 μs; intensity: 300 μA; 600 pulses in 10 min) or phasic (square waves at 100 Hz; pulse duration: 200 μs; intensity: 300 μA; 8 trains of 10 pulses at 1 min interval; 800 pulses in 10 min) stimulations applied into their VTA for 4 days. A single dose of PTZ was injected after each DBS. Simultaneously electrocorticography and video recordings were performed during the seizure for accuracy in seizure severity parameters detection. Tonic but not phasic stimulation significantly decreased the epileptiform discharge duration and the seizure behavioral parameters such as maximum seizure stage, stage 5 duration, seizure duration. In addition, focal to generalized seizure latency increased following VTA tonic stimulation. These data suggest that tonic (but not phasic) stimulation of VTA before PTZ injection on 4 test days had anticonvulsant effects on PTZ-kindled seizures.