Activation of SGK1.1 Upregulates the M-current in the Presence of Epilepsy Mutations

In the central nervous system, the M-current plays a critical role in regulating subthreshold electrical excitability of neurons, determining their firing properties and responsiveness to synaptic input. The M-channel is mainly formed by subunits Kv7.2 and Kv7.3 that co-assemble to form a heterotetrametric channel. Mutations in Kv7.2 and Kv7.3 are associated with hyperexcitability phenotypes including benign familial neonatal epilepsy (BFNE) and neonatal epileptic encephalopathy (NEE). SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), increases M-current density in neurons, leading to reduced excitability and protection against seizures. Herein, using two-electrode voltage clamp on Xenopus laevis oocytes, we demonstrate that SGK1.1 selectively activates heteromeric Kv7 subunit combinations underlying the M-current. Importantly, activated SGK1.1 increases M-channel activity in the presence of two different epilepsy mutations found in Kv7.2, R207W and A306T. In addition, proximity ligation assays in the N2a cell line allowed us to address the effect of these mutations on Kv7-SGK1.1-Nedd4 molecular associations, a proposed pathway underlying augmentation of M-channel activity by SGK1.1

Ion Channel Dysfunction and Neuroinflammation in Migraine and Depression

Migraine and major depression are debilitating disorders with high lifetime prevalence rates. Interestingly these disorders are highly comorbid and show significant heritability, suggesting shared pathophysiological mechanisms. Non-homeostatic function of ion channels and neuroinflammation may be common mechanisms underlying both disorders: The excitation-inhibition balance of microcircuits and their modulation by monoaminergic systems, which depend on the expression and function of membrane located K+, Na+, and Ca+2 channels, have been reported to be disturbed in both depression and migraine. Ion channels and energy supply to synapses not only change excitability of neurons but can also mediate the induction and maintenance of inflammatory signaling implicated in the pathophysiology of both disorders. In this respect, Pannexin-1 and P2X7 large-pore ion channel receptors can induce inflammasome formation that triggers release of pro-inflammatory mediators from the cell. Here, the role of ion channels involved in the regulation of excitation-inhibition balance, synaptic energy homeostasis as well as inflammatory signaling in migraine and depression will be reviewed.

Activation of SGK1.1 up-regulates the M-current in the presence of epilepsy mutations

In the central nervous system, the M-current plays a critical role in regulating subthreshold electrical excitability of neurons, determining their firing properties and responsiveness to synaptic input. The M-channel is mainly formed by subunits Kv7.2 and Kv7.3 that co-assemble to form a heterotetrametric channel. Mutations in Kv7.2 and Kv7.3 are associated with hyperexcitability phenotypes including benign familial neonatal epilepsy (BFNE) and neonatal epileptic encephalopathy (NEE). SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), increases M-current density in neurons, leading to reduced excitability and protection against seizures. Herein, using two-electrode voltage clamp on Xenopus laevis oocytes, we demonstrate that SGK1.1 selectively activates heteromeric Kv7 subunit combinations underlying the M-current. Importantly, activated SGK1.1 is able to up-regulate M-channel activity in the presence of two different epilepsy mutations found in Kv7.2 subunit, R207W and A306T. In addition, proximity ligation assays in the N2a cell line allowed us to address the effect of these mutations on Kv7-SGK1.1-Nedd4 molecular associations, a proposed pathway underlying M-channel up-regulation by SGK1.1

Effect of caffeine and coffee diets on calcium signalling in rat hippocampal neurons

The effects of long-lasting high concentration coffee and caffeine diets on calcium mobilization in rat hippocampal neurons were studied. Changes in the basal calcium level in the hippocampal neurons of control and experimental rats kept on a coffee or caffeine diet were measured. We also recorded the changes in the Ca2+ transients’ amplitude evoked by membrane depolarization or emptying the Ca2+ depot of the endoplasmic reticulum (ER) induced by caffeine activator of the ryanodine receptors. In rats on a coffee or caffeine diet, the basal Ca2+ level was increased by 7.4% and 11%, respectively, compared to control animals. In these groups, the amplitude of Ca2+ transients increased by 70% and 90%, respectively, of the basal level in response to the membrane depolarization. In the same groups, the amount of Ca2+ released from the ER was increased by two and three times, respectively, compared to the control after activation of ryanodine receptors. We concluded that long-term coffee and caffeine diets in rats cause a significant disruption of the hippocampal neurons’ endoplasmic reticulum function. The diets evoke an increase in Ca2+ concentration in the neurons and an excessive release of Ca2+ in response to excitation. The latter can lead to increased excitability of neurons and their further death from excessive Ca2+ levels.

Sodium Leak Channel in the Nucleus Accumbens Modulates Ethanol-Induced Acute Stimulant Responses and Locomotor Sensitization in Mice: A Brief Research Report

Ethanol can induce acute stimulant responses in animals and human beings. Moreover, repeated exposure to ethanol may produce increased sensitivity to its acute locomotor stimulant actions, a process referred to as locomotor sensitization. The molecular mechanism of the development of acute stimulant responses and locomotor sensitization by ethanol is not fully understood. Sodium leak channel (NALCN) is widely expressed in central nervous system and controls the basal excitability of neurons. The present study aims to determine whether NALCN is implicated in the ethanol-induced acute responses and locomotor sensitization in mice. Here, our results showed that ethanol caused acute stimulant responses in DBA/2 mice. Locomotor sensitization was successfully induced following the sensitization procedure. Accordingly, the expression levels of NALCN mRNA and protein in the nucleus accumbens (NAc) were markedly increased in the sensitization mice compared to the control mice. Knockdown the expression levels of NALCN in the NAc alleviated both the ethanol-induced acute responses and locomotor sensitization. Our findings indicate that upregulation of NALCN expression in the NAc contributes to the ethanol-induced acute stimulant responses and locomotor sensitization in DBA/2 mice.

Clinical Pharmacology and Therapeutics of Antiepileptic Drugs

This article describes clinical antiepileptic drugs (AEDs) that are available for treatment of epilepsy. Epilepsy is characterized by repeated occurrence of seizures. Epileptic seizures are classified into focal onset (partial) and generalized onset (generalized) types. Around two-dozen AEDs are available for treating epilepsy. AEDs act on diverse molecular targets to selectively modify the abnormal excitability of neurons by reducing the focal seizure discharges or preventing spread of excitation. AEDs suppress seizures by blocking the voltage-gated sodium channels (phenytoin, carbamazepine, valproate, lamotrigine, oxcarbazepine, topiramate), voltage-activated calcium channels (ethosuximide, gabapentin), potentiation of GABA inhibition (barbiturates, benzodiazepines, tiagabine), and reduction of glutamate excitation (felbamate, parampanel). Carbamazepine, phenytoin, and valproate are the first-line agents for partial onset seizures and generalized onset seizures. Ethosuximide is the drug of choice for absence seizures. AEDs are orally-active and show unique PK features. Some AEDs cause enzyme induction and hence produce drug-drug interactions. Newer AEDs such as gabapentin, levetiracetam, tiagabine, and pregabalin do not cause enzyme induction. Despite many advances in AEDs, nearly 30% of people with epilepsy have drug-resistant or intractable seizures. Presently, there is no cure for epilepsy. Thus, newer and better AEDs that can better prevent refractory seizures and modify the disease are needed for curing epilepsy.

NNC55-0396 Reduces SH-SY5Y Cell Damage Induced by Bupivacaine Hydrochloride

Background Local anesthetic neurotoxicity is a common complication in clinical anesthesia, which can cause permanent nerve damage in severe cases. The T-type calcium channel is an important channel for regulating the excitability of neurons. Normally, extracellular calcium ions enter the cell through the T-type calcium channel to change the excitability of neurons. When the intracellular calcium is overloaded, it can cause cell damage. Aims To investigated the roles of T-type calcium channel in the SH-SY5Y cells injury induced by the bupivacaine. Methods The SH-SY5Y cell culture model was used to observe the effect of T-type calcium channel blocker NNC55-0396 on the neurotoxicity of bupivacaine hydrochloride by MTT methold,flow cytometry, Western blotting and other methods. Results The results show that NNC55-0396 can block the T-type calcium channel of SH-SY5Y cells, improve the decrease of cell viability caused by bupivacaine hydrochloride, reduce the level of intracellular calcium ion, reduce the expression of Cleavedcaspase-3, and reduce cell apoptosis. Conclusion The above results indicate that the T-type calcium channel is involved in the SH-SY5Y cell damage caused by bupivacaine hydrochloride, and blocking the T-type calcium channel can reduce the neurotoxicity of bupivacaine hydrochloride.

Dual stochasticity in the cortex as a biologically plausible learning with the most efficient coding

Neurons and synapses in the cerebral cortex behave stochastically. The advantages of such stochastic properties have been proposed in several works, but the relationship and synergy between the stochasticities of neurons and synapses remain largely unexplored. Here, we show that these stochastic features can be inseparably integrated into a simple framework that provides a practical and biologically plausible learning algorithm that consistently accounts for various experimental results, including the most efficient power-law coding of the cortex. The derived algorithm overcomes many of the limitations of conventional learning algorithms of neural networks. As an experimentally testable prediction, we derived the slow retrograde modulation of the excitability of neurons from this algorithm. Because of the simplicity and flexibility of this algorithm, we anticipate that it will be useful in the development of neuromorphic devices and scalable AI chips, and that it will help bridge the gap between neuroscience and machine learning.