Summary: Researchers have produced a high-resolution, cell-by-cell atlas of the amygdala, revealing unexpected links between neuronal energy metabolism and addiction behaviors—and pointing to a potential therapeutic target for cocaine use disorder.
A single-cell examination of the amygdala, a compact but critical brain region that governs emotional responses, has uncovered novel molecular connections between susceptibility to cocaine addiction and genes that regulate cellular energy. The study suggests that how neurons manage energy may influence addiction-like behaviors and relapse vulnerability.
Using single-nucleus sequencing, the research team profiled gene expression and chromatin accessibility in individual amygdala cells from outbred rats with divergent cocaine addiction–like behaviors. This approach produced a detailed molecular atlas of the rat amygdala and provided fresh insights into the biology underlying cocaine addiction.
The results indicate that preexisting genetic differences may predispose some individuals to addiction, and that pharmacological modulation of an enzyme involved in energy metabolism and neuronal signaling can reverse addiction-related behaviors in animals. These findings move the field closer to personalized interventions for substance use disorders.
Key Facts:
- Cell-by-cell amygdala atlas: Single-nucleus sequencing produced a comprehensive molecular map of the rat amygdala, revealing cell-type–specific gene programs linked to addiction vulnerability.
- Energy metabolism link: Differentially expressed genes between high- and low-addiction groups were enriched for pathways involved in cellular energy metabolism, implicating metabolic regulation in addiction biology.
- Therapeutic proof-of-concept: Pharmacological inhibition of the glyoxalase 1 enzyme—an enzyme tied to glycolysis and neuronal signaling—reversed increased relapse-like behaviors and altered GABAergic transmission in high-addiction rats, suggesting a possible treatment avenue.
Source: UCSD
Researchers at the University of California San Diego School of Medicine and the Salk Institute for Biological Studies have assembled a unique single-cell atlas of the amygdala, revealing molecular features that influence emotional responses to drugs.
Published October 5, 2023 in Nature Neuroscience, the study addresses a critical gap: there are no approved, safe, and effective pharmacological treatments for cocaine addiction, despite its severe public health impact. The work identifies molecular signatures that distinguish animals with high versus low addiction-like behaviors and tests a compound that modifies those behaviors.
“While medications exist for some substance use disorders, such as nicotine and opioid dependence, there are currently no approved drugs for cocaine addiction,” said co-senior author Francesca Telese, PhD, associate professor in the Department of Psychiatry at UC San Diego School of Medicine. “Our findings point to molecular mechanisms that were previously unappreciated and may be common across different forms of addiction.”
Cocaine use remains a major concern: many people use the drug recreationally, but not all develop addiction. According to national estimates, millions used cocaine in recent years while a smaller subset met criteria for cocaine use disorder. Understanding why some individuals are more vulnerable to addiction than others was a central aim of this work.
The researchers analyzed brain samples from rats that had self-administered cocaine over extended sessions and then experienced a period of abstinence. These specimens were sourced from a specialized cocaine brain bank maintained at UC San Diego by co-authors Abraham A. Palmer, PhD, and Olivier George, PhD.
“The cocaine brain bank gave us access to a genetically diverse cohort of rats, which better mirrors human population variability,” Telese explained. “Using a self-administration model allowed us to directly connect molecular differences to real addiction-related behaviors.”
To parse the large sequencing dataset, the team collaborated with bioinformatics experts at the Salk Institute. Graham McVicker, PhD, and graduate student Jess Zhou developed the computational workflow needed to assemble gene expression and chromatin accessibility data into an integrated amygdala atlas.
Analysis revealed consistent enrichment of energy metabolism pathways among genes that differed between high- and low-addiction animals across multiple cell types. High-addiction rats also displayed elevated relapse-like behaviors and increased GABAergic transmission in the amygdala. Targeting glyoxalase 1, an enzyme that metabolizes methylglyoxal (a glycolysis-derived modulator of GABAA receptors), normalized both the behavioral and physiological differences.
“Linking cellular-level molecular signatures to behavior—and showing we can modify those behaviors pharmacologically—advances our understanding of the complex brain mechanisms that drive addiction and relapse,” Telese said.
The team plans follow-up studies with larger sample sizes to disentangle the contributions of inherent genetic variation from changes induced by prolonged cocaine exposure. Clarifying these factors will be essential for tailoring interventions to individuals’ biological risk profiles.
“Our data suggest that preexisting genetic differences may play a larger role in addiction susceptibility than previously appreciated,” Telese added. “Decoding these genetic influences is critical for developing personalized strategies to reduce relapse risk.”
Co-authors include Giordano de Guglielmo, Marsida Kallupi, Narayan Pokhrel, Apurva S. Chitre, Daniel Munro, Hai-Ri Li, Lieselot LG Carrette (UC San Diego), Aaron J. Ho (Salk Institute), and Pejman Mohammadi (Scripps Research and University of Washington).
About this brain mapping and addiction research news
Author: Miles Martin
Source: UCSD
Contact: Miles Martin – UCSD
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Single-nucleus genomics in outbred rats with divergent cocaine addiction-like behaviors reveals changes in gene amygdala GABAergic inhibition” by Telese et al., Nature Neuroscience
Abstract
Single-nucleus genomics in outbred rats with divergent cocaine addiction-like behaviors reveals changes in gene amygdala GABAergic inhibition
The amygdala encodes positive and negative valence and contributes to addiction, yet the cell-type–specific gene regulatory programs that underlie this contribution are not well defined. We generated an atlas of single-nucleus gene expression and chromatin accessibility in the amygdala of outbred rats that displayed high or low cocaine addiction–like behaviors after prolonged abstinence.
Differentially expressed genes between high- and low-addiction-index groups were enriched for energy metabolism pathways across multiple cell types. Rats with a high addiction index exhibited increased relapse-like behaviors and enhanced GABAergic transmission in the amygdala. Both behavioral and physiological phenotypes were reversed by pharmacological inhibition of glyoxalase 1, an enzyme that metabolizes methylglyoxal—a glycolysis-derived molecule that acts as a GABAA receptor agonist.
Chromatin accessibility differences between high- and low-addiction-index rats implicated pioneer transcription factors from the basic helix-loop-helix, FOX, SOX, and activator protein 1 families. We observed cell-type–specific and often opposite regulation of chromatin accessibility: notably, excitatory neurons showed greater accessibility in high-addiction-index rats, while inhibitory neurons showed greater accessibility in low-addiction-index rats.