Summary: New research maps how cocaine changes gene activity across the brain’s reward system, revealing stage-specific molecular signatures that could inform future treatments for addiction.
Source: Elsevier.
Researchers report in Biological Psychiatry that cocaine self-administration produces distinct, region-specific changes in gene expression across the brain’s reward circuitry. The study captures molecular responses to initial use, withdrawal, and re-exposure after prolonged abstinence, providing a comprehensive transcriptome-level view of how voluntary cocaine intake reshapes the brain.
Using a mouse model in which animals self-administer cocaine, the team linked alterations in gene expression to measurable addiction-like behaviors. Their approach went beyond previous work by surveying multiple interconnected reward regions simultaneously and by tracking gene expression at several time points across the addiction cycle.
“This study elegantly highlights the complexity of the brain’s molecular response to self-administered cocaine, pointing to mechanisms that might be targeted by treatments,” said John Krystal, Editor of Biological Psychiatry.
Previous molecular studies of cocaine addiction tended to be narrow in scope, examining only specific genes or isolated brain regions. That approach left unanswered how cocaine alters gene networks across the whole reward circuit and how those changes evolve during use, withdrawal, and relapse. The new study addresses this gap by profiling the global transcriptome in six key reward-related brain regions across the full life cycle of cocaine self-administration.
Lead author Eric Nestler, MD, PhD, of the Icahn School of Medicine at Mount Sinai, explained that the study’s design enabled tracking of time-dependent, region-specific transcriptional changes produced by voluntary drug intake. The researchers examined gene expression during first exposure to cocaine, after short (24-hour) and long (30-day) withdrawal periods, and following re-exposure to cocaine after the extended withdrawal period.
The experiments revealed widespread but nuanced transcriptional reprogramming. Many transcripts involved in neuronal signaling, plasticity, and stress-response pathways were altered, and several changes were consistent across multiple reward regions—making them attractive candidates for therapeutic targeting. Other changes were region-specific or dependent on the stage of the addiction cycle, demonstrating that the molecular landscape of addiction dynamically shifts between initial use, abstinence, and relapse.
Importantly, the magnitude and direction of gene expression changes depended on the specific condition: whether the mice were experiencing acute cocaine exposure, contextual re-exposure, or combined drug-and-context re-exposure after prolonged withdrawal. By integrating behavioral measures into their analysis, the team identified gene sets whose expression correlated with an addiction index—a composite score derived from several addiction-like behaviors during cocaine self-administration—revealing molecular signatures linked to behavioral vulnerability.
Further analysis pinpointed likely upstream regulators of these transcriptional responses. Families of transcriptional regulators, including cyclic adenosine monophosphate response element binding protein (CREB) and several nuclear receptors, emerged as key drivers of the gene networks associated with addiction-related behaviors. These regulators could serve as strategic nodes for interventions aimed at normalizing dysregulated gene expression across the reward circuit.
The authors emphasize that the study does not present a single unified “addiction gene,” but rather describes a complex, region-dependent reorganization of transcriptional programs that unfold over time. By documenting these patterns across multiple brain regions and behavioral states, the research provides a rich resource for investigators seeking molecular targets to prevent or reverse cocaine-driven changes in the brain.
Source: Rhiannon Bugno — Elsevier
Publisher: Organized by Neuroscience News.
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Original Research: Abstract for “Cocaine Self-administration Alters Transcriptome-wide Responses in the Brain’s Reward Circuitry” by Deena M. Walker, Hannah M. Cates, Yong-Hwee E. Loh, Immanuel Purushothaman, Aarthi Ramakrishnan, Kelly M. Cahill, Casey K. Lardner, Arthur Godino, Hope G. Kronman, Jacqui Rabkin, Zachary S. Lorsch, Philipp Mews, Marie A. Doyle, Jian Feng, Benoit Labonté, Ja Wook Koo, Rosemary C. Bagot, Ryan W. Logan, Marianne L. Seney, Erin S. Calipari, Li Shen, and Eric J. Nestler in Biological Psychiatry. Published April 25, 2018.
DOI: 10.1016/j.biopsych.2018.04.009
Abstract (summary)
Background
Global, coordinated changes in gene expression that underlie circuit and behavioral dysregulation in cocaine addiction are incompletely understood. This study mapped how a history of voluntary cocaine use reshapes transcriptome-wide responses throughout the brain’s reward circuitry at baseline and after context- and drug-related re-exposure following prolonged withdrawal.
Methods
Male mice were assigned to groups representing different stages of cocaine exposure: initial saline or cocaine self-administration; short withdrawal (24 hours); or long withdrawal (30 days) followed by an acute saline or cocaine challenge in the drug-paired context. RNA sequencing was performed on six interconnected reward regions. Pattern analysis of gene expression and factor analysis of behavior identified genes strongly associated with addiction-related behaviors and altered by prior cocaine self-administration. Potential upstream regulators were then predicted.
Results
Three dominant gene expression patterns reflecting responses to acute cocaine, context re-exposure, and combined drug-plus-context re-exposure were described, with clear region-specific regulation. Each pattern correlated with the behavioral addiction index in a region-dependent way. CREB and several nuclear receptor families were identified as probable upstream regulators of behavior-linked gene networks.
Conclusions
This transcriptome-wide atlas of cocaine-induced regulation across the brain’s reward circuitry and across withdrawal stages deepens understanding of the molecular basis of cocaine addiction and will inform future studies of targeted molecular pathways.