Does retigabine affect the development of alcohol dependence?--A pharmaco-EEG study

The role of KCNQ channel activators in management of major depressive disorder

Depression, a complex disorder with significant treatment challenges, necessitates innovative therapeutic approaches to address its multifaceted nature and enhance treatment outcomes. The modulation of KCNQ potassium (K+) channels, pivotal regulators of neuronal excitability and neurotransmitter release, is a promising innovative therapeutic target in psychiatry. Widely expressed across various tissues, including the nervous and cardiovascular systems, KCNQ channels play a crucial role in modulating membrane potential and regulating neuronal activity. Recent preclinical evidence suggests that KCNQ channels, particularly KCNQ3, contribute to the regulation of neuronal excitability within the reward circuitry, offering a potential target for alleviating depressive symptoms, notably anhedonia. Studies using animal models demonstrate that interventions targeting KCNQ channels can restore dopaminergic firing balance and mitigate depressive symptoms. Human studies investigating the effects of KCNQ channel activators, such as ezogabine, have shown promising results in alleviating depressive symptoms and anhedonia. The aforementioned observations underscore the therapeutic potential of KCNQ channel modulation in depression management and highlight the need and justification for phase 2 and phase 3 dose-finding studies as well as studies prespecifying symptomatic targets in depression including anhedonia.

Biomedical Research on Substances of Abuse: The Italian Case Study

Substances of abuse have the potential to cause addiction, habituation or altered consciousness. Most of the research on these substances focuses on addiction, and is carried out through observational and clinical studies on humans, or experimental studies on animals. The transposition of the EU Directive 2010/63 into Italian law in 2014 (IT Law 2014/26) includes a ban on the use of animals for research on substances of abuse. Since then, in Italy, public debate has continued on the topic, while the application of the Article prohibiting animal research in this area has been postponed every couple of years. In the light of this debate, we briefly review a range of methodologies - including animal and non-animal, as well as patient or population-based studies - that have been employed to address the biochemical, neurobiological, toxicological, clinical and behavioural effects of substances of abuse and their dependency. We then discuss the implications of the Italian ban on the use of animals for such research, proposing concrete and evidence-based solutions to allow scientists to pursue high-quality basic and translational studies within the boundaries of the regulatory and legislative framework.

Beneficial effect of retigabine on memory in rats receiving ethanol

Background

Retigabine belongs to the novel generation of antiepileptic drugs but its complex mechanism of action causes that the drug might be effective in other diseases, for instance, alcohol dependence. It is known that ethanol abuse impaired the function of brain structures associated with memory and learning such as the hippocampus. In our previous study, retigabine reduced hippocampal changes induced by ethanol in the EEG rhythms in rabbits. This study is focused on the impact of retigabine on memory processes in male rats receiving alcohol.

Methods

Memory was evaluated in various experimental models: Morris water maze, Contextual, and Cued Fear Conditioning tests. Retigabine was administered for 3 weeks directly to the stomach via oral gavage at a dose of 10 mg/kg. Rats received also 20% ethanol (5 g/kg/day in two doses) via oral gavage for 3 weeks and had free access to 5% ethanol in the afternoon and at night. Morris water maze was performed after 1 and 3 weeks of ethanol administration and after 1 week from the discontinuation of ethanol administration. Contextual and Cued Fear Conditioning tests were carried out after 24 h and 72 h of alcohol discontinuation.

Results

The drug significantly decreased ethanol-induced memory disturbances during alcohol administration as well as slightly improved learning processes after the discontinuation of ethanol administration.

Conclusions

This beneficial effect of retigabine-ethanol interaction on memory may be a relevant element of the drug’s impact on the development of addiction.

Identification and validation of midbrain Kcnq4 regulation of heavy alcohol consumption in rodents

Currently available pharmacotherapies for treating alcohol use disorder (AUD) suffer from deleterious side effects and are not efficacious in diverse populations. Clinical and preclinical studies provide evidence that the Kcnq family of genes that encode K_V7 channels influence alcohol intake and dependence. K_V7 channels are a class of slowly activating voltage-dependent K⁺ channels that regulate neuronal excitability. Studies indicate that the K_V7 channel positive modulator retigabine can decrease dopaminergic neuron firing, alter dopamine (DA) release, and reduce alcohol intake in heavy drinking rodents. Given the critical nature of ventral tegmental area (VTA) DA to the addiction process and predominant expression of Kcnq4 in DA neurons, we investigated the role of midbrain Kcnq genes and K_V7 channels in the VTA of genetically diverse mice and long-term heavy drinking rats, respectively. Integrative bioinformatics analysis identified negative correlations between midbrain Kcnq4 expression and alcohol intake and seeking behaviors. Kcnq4 expression levels were also correlated with dopaminergic-related phenotypes in BXD strains, and Kcnq4 was present in support intervals for alcohol sensitivity and alcohol withdrawal severity QTLs in rodents. Pharmacological validation studies revealed that VTA K_V7 channels regulate excessive alcohol intake in rats with a high-drinking phenotype. Administration of a novel and selective K_V7.2/4 channel positive modulator also reduced alcohol drinking in rats. Together, these findings indicate that midbrain Kcnq4 expression regulates alcohol-related behaviors in genetically diverse mice and provide evidence that K_V7.4 channels are a critical mediator of excessive alcohol drinking.

Chronic Alcohol, Intrinsic Excitability, and Potassium Channels: Neuroadaptations and Drinking Behavior

Neural mechanisms underlying alcohol use disorder remain elusive, and this lack of understanding has slowed the development of efficacious treatment strategies for reducing relapse rates and prolonging abstinence. While synaptic adaptations produced by chronic alcohol exposure have been extensively characterized in a variety of brain regions, changes in intrinsic excitability of critical projection neurons are understudied. Accumulating evidence suggests that prolonged alcohol drinking and alcohol dependence produce plasticity of intrinsic excitability as measured by changes in evoked action potential firing and after-hyperpolarization amplitude. In this chapter, we describe functional changes in cell firing of projection neurons after long-term alcohol exposure that occur across species and in multiple brain regions. Adaptations in calcium-activated (K_Ca2), voltage-dependent (K_V7), and G protein-coupled inwardly rectifying (K_ir3 or GIRK) potassium channels that regulate the evoked firing and after-hyperpolarization parallel functional changes in intrinsic excitability induced by chronic alcohol. Moreover, there are strong genetic links between alcohol-related behaviors and genes encoding K_Ca2, K_V7, and GIRK channels, and pharmacologically targeting these channels reduces alcohol consumption and alcohol-related behaviors. Together, these studies demonstrate that chronic alcohol drinking produces adaptations in K_Ca2, K_V7, and GIRK channels leading to impaired regulation of the after-hyperpolarization and aberrant cell firing. Correcting the deficit in the after-hyperpolarization with positive modulators of K_Ca2 and K_V7 channels and altering the GIRK channel binding pocket to block the access of alcohol represent a potentially highly effective pharmacological approach that can restore changes in intrinsic excitability and reduce alcohol consumption in affected individuals.

The Impact of Zonisamide on the Development and Course of Alcohol Dependence in Rabbits. A pharmaco-EEG study

Aims

Zonisamide is a new anti-epileptic drug whose mechanism of action is associated with neurotransmission systems also involved in the pathogenesis of addiction. Recently, the role of memory processes and the hippocampus (Hp) is underlined in dependence. In our previous study, we determined that zonisamide decreases changes in hippocampal bioelectric activity induced by a single dose of ethanol.

Methods

This study uses a pharmaco-EEG method to examine the impact of zonisamide on the development and course of alcohol dependence in rabbits. Quantitative changes in EEG were observed in the midbrain reticular formation, Hp and frontal cortex. Zonisamide was administered p.o. once a day at dose of 30 mg/kg/day during the entire experiment. Solutions with increasing concentrations of ethanol were administered for 6 weeks, followed by a 2-week period of abstinence.

Results

The long-term administration of ethanol caused characteristic changes in rabbit EEG recordings, which were associated with a shift toward lower frequencies resulting in a depressive effect on the bioelectric activity of selected brain structures. Co-administration of zonisamide and ethanol caused a reduction of ethanol-induced alterations. Changes in EEG recordings were different during period of abstinence and were associated with potent shift toward the high frequencies. Zonisamide significantly decreased encephalographic features of neuronal hyperactivity when administered during the abstinence.

Conclusion

Zonisamide decreases ethanol- and abstinence-induced changes in the EEG recordings. These effects may be a significant part of drug's mechanism of action in alcohol addiction therapy.

Short Summary

A pharmaco-EEG method was used to determine the influence of a new anti-epileptic drug zonisamide on the development and course of alcohol dependence in rabbits. The drug co-administered with ethanol decreased alcohol-induced changes in selected brain structures. Zonisamide also decreases abstinence-induced changes in the EEG recordings.