Receptors and Channels Associated with Alcohol Use: Contributions from Drosophila

Leucine-rich repeat kinase 2 limits dopamine D1 receptor signaling in striatum and biases against heavy persistent alcohol drinking

The transition from hedonic alcohol drinking to problematic drinking is a hallmark of alcohol use disorder that occurs only in a subset of drinkers. This transition requires long-lasting changes in the synaptic drive and the activity of striatal neurons expressing dopamine D1 receptor (D1R). The molecular mechanisms that generate vulnerability in some individuals to undergo the transition are less understood. Here, we report that the Parkinson's-related protein leucine-rich repeat kinase 2 (LRRK2) modulates striatal D1R function to affect the behavioral response to alcohol and the likelihood that mice transition to heavy, persistent alcohol drinking. Constitutive deletion of the Lrrk2 gene specifically from D1R-expressing neurons potentiated D1R signaling at the cellular and synaptic level and enhanced alcohol-related behaviors and drinking. Mice with cell-specific deletion of Lrrk2 were more prone to heavy alcohol drinking, and consumption was insensitive to punishment. These findings identify a potential novel role for LRRK2 function in the striatum in promoting resilience against heavy and persistent alcohol drinking.

An Ant-Mimicking Jumping Spider Achieves Higher Predation Probability with Lower Success Rate When Exposed to Ethanol

Ethanol (ETOH) affects many animals' behaviour in nature; for example, honeybees become more aggressive after consuming ETOH. In previous studies, scientists have used honeybees and fruit flies as models to determine if they showed a strong preference to ETOH. Moreover, ETOH could affect their locomotion and learning abilities. However, whether and how ETOH affects spiders is unclear as of yet. In this study, we used empirical experiments to determine whether spiders showed preference for ETOH, as well as the potential benefits of spiders choosing ETOH, by using a common spider, Myrmarachne gisti, which has a high probability of contacting ETOH in their habitat. In our experiment, M. gisti showed a significant preference for ETOH. Although the success rate of the first attack was significantly decreased when M. gisti were exposed to ETOH, they had a significantly higher predation probability, since fruit flies also showed a significant preference for ETOH. Our findings suggested that ETOH could affect the prey capture efficiency of M. gisti, and indicated that spiders might evolve to use ETOH to locate a potential hunting place. Taken together, our findings suggested that M. gisti evolved to adapt to ETOH and could use it as a signal of the presence of food resources.

Agomelatine attenuates alcohol craving and withdrawal symptoms by modulating the Notch1 signaling pathway in rats

AIM

Alcohol abuse is a significant causative factor of death worldwide. The Notch1 signaling pathway is involved in alcohol tolerance, withdrawal and dependence. Agomelatine is a known antidepressant acting as a melatonin receptor (MT1/2) agonist and a 5-hydroxytryptamine receptor-2C antagonist. However, its effects on alcohol cravings and alcohol withdrawal symptoms have not been investigated. In this study, we assessed the possibility of using agomelatine for the treatment of these symptoms in a rat model of alcoholism and the possible role of Notch1 signaling.

MAIN METHODS

We induced alcoholism in rats using a free-choice drinking model for 60 days. From day 61, free-choice was continued until day 82 for the craving model, whereas only water was offered in the withdrawal model. Meanwhile, the treated groups for both models received agomelatine (50 mg/kg/day) orally from day 61 to 82, followed by behavioral, histopathological and biochemical assessment.

KEY FINDINGS

Agomelatine treatment caused significant decrease in alcohol consumption with a positive effect on anxiety-like behavior in the open field, memory in the Morris water maze and immobility in the forced swim test. Moreover, agomelatine induced the expression of Notch1 pathway markers, including Notch1, NICD, CREB, CCNE-2, Hes-1, both total and phosphorylated ERK1/2, MMP9, Per2and RGS-2 in the hippocampal formation. By contrast, NMDAR expression was reduced. Furthermore, agomelatine normalized the serum levels of BDNF, cortisol, dopamine and glutamate which were disrupted by alcohol consumption.

SIGNIFICANCE

Based on these findings, agomelatine reversed alcohol cravings and withdrawal symptoms associated with alcohol dependence by modulating the Notch1 signaling pathway.