Effects of N-acetylcysteine after repeated exposure to ethanol in memory and neurotransmission in zebrafish

Introduction

In the brain, alcohol metabolites alter the functioning of several neurotransmission systems, such as glutamatergic and cholinergic, in addition to impairing memory and learning. Medications for Alcohol Use Disorders (AUD) cause adverse effects and contraindications. N-acetylcysteine (NAC) has been shown to protect memory and restore acetylcholinesterase (AChE) levels. Additionally, it functions as an antioxidant that works alongside glutathione, which is associated with the glutamatergic synapse. In this context, the current research aimed to examine the neuroprotective effects of NAC in animals that underwent repeated ethanol exposure (REE), along with the impacts on memory and the cholinergic and glutamatergic signaling pathways in zebrafish.

Methods

The animals were exposed to 1 % ethanol for 8 days for 20 min daily. They received treatment with NAC after the eighth exposure to ethanol for 10 or 60 min. Euthanasia occurred 24 h after the last exposure. Inhibitory avoidance and object recognition tests were performed. Also, the choline acetyltransferase (ChAT) enzyme activities, AChE activity, and glutamate uptake were evaluated.

Results

The results show a significant AChE activity increase in the REE group and a decrease in those exposed to alcohol and treated with NAC for 10 min. No significant differences were found regarding ChAT activity. REE significantly reduced glutamate uptake. All groups except the ethanol group acquired aversive memory in inhibitory avoidance tests. Only the NAC-treated group demonstrated longer new object exploration in the recognition test. The study indicates that REE affects AChE, glutamate uptake, and aversive memory and that a single NAC treatment can mitigate these effects. These findings enhance the understanding of REE mechanisms and NAC's protective properties against ethanol-induced damage in zebrafish.