Treadmill Exercise Reshapes Cortical Astrocytic and Neuronal Activity to Improve Motor Learning Deficits Under Chronic Alcohol Exposure

Background and Research Motivation

Alcohol abuse is a global health issue, affecting over 8% of the male population. Prolonged alcohol exposure can alter the homeostasis of neurons and synapses in the brain, leading to various mental disorders and cognitive deficits, especially in motor learning. Previous studies have shown that alcohol abuse causes significant neuronal degeneration and synaptic loss, severely impacting cortical and subcortical functions. Furthermore, research has found that apart from neurons, glial cells also undergo significant changes under the influence of alcohol. There is mention in the literature that alcohol abuse leads to altered microglial signaling and impaired oligodendrocyte lineage differentiation, but there is still insufficient in vivo evidence regarding the changes in neuronal and glial cell activities.

This study aims to explore the role of motor training in the recovery of cortical neuron and astrocyte functions by establishing a chronic alcohol exposure mouse model, utilizing sustained treadmill training and in vivo imaging techniques. This research hopes to reveal the potential of motor training in improving motor learning deficits and synapse formation due to alcohol exposure, thus providing new scientific evidence for the rehabilitation of alcohol abuse.

Introduction of the Paper

The paper, titled “Treadmill Exercise Reshapes Cortical Astrocytic and Neuronal Activity to Improve Motor Learning Deficits Under Chronic Alcohol Exposure,” was co-authored by scholars Linglin Liu, Lanzhi Luo, Ji-An Wei, Xintong Xu, Kwok-Fai So, and Li Zhang. The study was supported by the Key Laboratory of Central Nervous System Regeneration under the Ministry of Education of China, Li Ka Shing Faculty of Medicine, The University of Hong Kong, and other institutions. It was officially published in the “Neuroscience Bulletin” in February 2024.

Detailed Content of the Study

Research Process

1. Preparation of Experimental Animals

   The experimental animals used were 5-6-week-old male C57BL/6J mice and Thy1-YFP mice, all sourced from the Guangdong Medical Experimental Animal Center and bred in the laboratory. Additionally, various viral vectors were obtained for injection and transgenic operations for subsequent optical imaging and gene expression experiments.

2. Chronic Alcohol Exposure Model

   To establish a chronic alcohol exposure model, mice were given intraperitoneal injections of 1000 mg/kg alcohol (anhydrous ethanol) daily for 18 consecutive days. Control group mice were injected with equivalent amounts of saline.

3. Treadmill Training

   Half of the alcohol-exposed mice were arranged on a treadmill for 1-hour daily training at speeds ranging from 8-12 meters/minute, continuing for the same 18 days. Mice in the control group were placed on the treadmill apparatus but did not undergo actual running training.

4. Stereotactic Injection of Viral Vectors

   Viral vectors (such as AAV-GFAP-GCaMP6s) were stereotactically injected to label calcium signals in neurons and astrocytes in the mouse motor cortex. After injection, a recovery period was allowed to ensure the effectiveness and stability of viral expression.

5. Behavioral Testing

   Various behavioral tests were used to assess the mice’s motor learning ability and late-stage behavior, including open-field tests, elevated plus maze tests, accelerating rotarod tests, and pole climbing tests. These tests provide crucial evidence for the impact of alcohol exposure and its effects under motor training.

Main Results

1. Alleviation of Motor Learning Deficits

   In motor learning tests, mice exposed to alcohol for 18 days exhibited significant declines in motor learning functions, such as poorer performance in the rotarod test and pole climbing test. However, mice that underwent sustained treadmill training showed significant improvements in these motor learning deficits.

2. Adjustment of Synaptic Structure and Function

   In vivo two-photon imaging revealed that alcohol treatment led to reduced synaptic density and lower rates of synapse formation and disappearance in the motor cortex of mice. These indicators recovered in trained mice, demonstrating the positive regulatory effect of motor training on synaptic structure and function.

3. Recovery of Neuronal Calcium Signals

   Calcium imaging results showed that the alcohol exposure group exhibited decreased overall calcium activity and peak calcium transients. However, after treadmill training, calcium activity significantly recovered. Notably, training effectively reduced neuron synchronization induced by alcohol.

4. Regulation of Astrocyte Activity

   Alcohol exposure significantly increased calcium activity in astrocytes, but treadmill training restored their activity levels to the normal range. Additionally, structural changes in astrocytes revealed that alcohol exposure caused increased cell body volume and excessive process formation, whereas motor training alleviated these overreactions, restoring normal morphology.

Research Conclusions and Significance

This study provides the first detailed evidence of the restorative effects of motor training on the central nervous system, particularly in the motor cortex region under alcohol abuse. By revealing how motor training modulates interactions between neurons and astrocytes to improve motor learning impairments caused by alcohol, the study demonstrates the potential application value of endurance exercise in the rehabilitation of alcohol abuse. The study also highlights the crucial role of astrocytes in motor training, further deepening the understanding of astrocyte-neuron interactions in synaptic plasticity and learning and memory functions.

Highlights and New Insights

1. Exploring the Role of Astrocytes in Alcohol Abuse and Rehabilitation

   This study revealed that astrocytes play crucial roles not only in alcohol abuse but also in synapse formation and neural activity regulation during motor training rehabilitation.

2. Validation of Motor Training Effects through Multiple Behavioral Tests

   Through various behavioral tests, including open-field tests, elevated plus maze tests, rotarod tests, and pole climbing tests, the effectiveness of treadmill training in improving alcohol-induced motor learning deficits was comprehensively validated.

3. Application of Advanced In Vivo Imaging Techniques to Trace Cellular Activities

   By using two-photon calcium imaging technology, dynamic activity changes of neurons and astrocytes under different experimental treatments were detailed, providing high-resolution data support for understanding cellular activity patterns.

4. Proposing New Mechanisms for Rehabilitation Interventions

   The study discovered that motor training improves synaptic formation and function by regulating astrocyte-neuron interactions, providing scientific evidence for developing new rehabilitation strategies for alcohol abuse.

Research Limitations and Future Outlook

Despite revealing the potential mechanisms of motor training in the rehabilitation of alcohol abuse, this study has certain limitations. For instance, it only used male mouse models; future studies should include female mice to explore sex differences. In addition, the effects of motor training on other brain regions such as the cerebellum and striatum in alcohol abuse and rehabilitation are also worthwhile areas for further research. Future studies could further analyze metabolic and molecular mechanism changes induced by motor training to comprehensively understand the underlying mechanisms of exercise in mitigating the effects of alcohol abuse.