Hippocampal fear engrams modulate ethanol-induced maladaptive contextual generalization in mice

Area of Science:

• Neuroscience
• Behavioral Science
• Pharmacology

Background:

• Alcohol use disorder (AUD) and co-occurring mental health disorders involve complex neurobiological interactions.
• The precise mechanisms underlying these maladaptive processes remain largely elusive.
• Fear processing deficits are a significant concern in AUD.

Purpose of the Study:

• To investigate the impact of chronic ethanol exposure on fear processing and generalization in mice.
• To develop and test an optogenetic strategy to rescue maladaptive fear responses in an AUD model.
• To elucidate the neural circuitry linking ethanol exposure, fear memory, and AUD.

Main Methods:

• Utilized a chronic ethanol administration and forced abstinence paradigm in male C57BL/6 mice.
• Employed optogenetics to target and inhibit specific neural ensembles in the dorsal hippocampus.
• Used an activity-dependent tet-tag system to label neurons activated during contextual fear conditioning.
• Assessed fear acquisition, contextual generalization, and behavioral responses during novel environment exposure.

Main Results:

• Ethanol-exposed mice exhibited potentiated fear acquisition and maladaptive contextual generalization.
• Optogenetic inhibition of fear-conditioned neural ensembles during novel environment exposure suppressed maladaptive generalization.
• Demonstrated cellular and behavioral evidence linking ethanol exposure to impaired fear memory processing.

Conclusions:

• Chronic ethanol exposure disrupts normal fear processing and enhances generalization.
• Targeted optogenetic intervention in the dorsal hippocampus can ameliorate maladaptive fear generalization in an AUD context.
• Findings provide crucial insights into the neural circuitry underlying AUD and associated fear processing deficits.