Chaloux-Pinette, E. | bioRxiv Science

bioRxiv2025

Transcriptional response to chronic long-access fentanyl self-administration in rat habenula and amygdala

Fentanyl is a potent synthetic opioid associated with overdose. However, little is known about fentanyl-induced molecular adaptations in the habenula and amygdala, two brain regions implicated in opioid use and withdrawal. We performed bulk RNA-sequencing in the rat habenula and amygdala to identify transcriptomic changes associated with fentanyl intake. Rats self-administered intravenous saline or fentanyl over 22-24 days. Ninety minutes following the final session, brains were collected for transcriptomic profiling. In Hb, we identified 453 differentially expressed genes (DEGs) between saline and fentanyl rats, with upregulated genes associated with synaptic transmission and ionic conductance. In amygdala, we identified 3,041 fentanyl-associated DEGs with upregulated genes implicated in metabolic and vesicular functions. Downregulated genes in both regions were enriched for extracellular matrix functions. Integration of DEGs with single-cell RNA-sequencing data from rodents and humans revealed that fentanyl DEGs were enriched in specific habenula and amygdala cell type markers. Furthermore, fentanyl downregulated DEGs in amygdala were enriched in genes associated with risk for substance use disorders. Together, we define how fentanyl intake alters transcriptional programs in the rat habenula and amygdala, and we link these changes to specific human cell types and risk genes for neuropsychiatric disorders and addiction.

neuroscience↗

bioRxiv2024

Optogenetic Central Amygdala Stimulation is Highly Reinforcing and Strongly Outcompetes Fentanyl Self-Administration in Male, but not Female, Rats

The central nucleus of the amygdala plays a key role in many aspects of substance use disorders, in particular biasing behaviors toward one drug or natural reward over another, yet the role of this region in opioid self-administration remains unclear. Here, we report that pharmacological inactivation of the central amygdala reduces fentanyl self-administration, while intra-central amygdala opioid receptor antagonism dose-dependently increases fentanyl self-administration. We tested whether optogenetic activation of the central amygdala would increase motivation for fentanyl in rats with a long fentanyl self-administration history. While pairing fentanyl delivery with optogenetic central amygdala activation increased fentanyl self-administration, optoactivation itself was highly reinforcing and, in choice settings, was pursued over fentanyl despite mounting effort requirements, delays, and sporadic reward availability. Of note, under free response conditions, these effects were limited to male rats; while female rats avidly responded for optogenetic activation of the central amygdala, this activation was less effective in enhancing fentanyl intake, and it was not preferred over fentanyl. In contrast, under discrete trial choice which precluded independent regulation of intake of the two options, both females and males preferred optoactivation to fentanyl. These results demonstrate that optogenetic stimulation of neural activity within the anterior central amygdala does not appear to potentiate the reinforcing effects of fentanyl, but is itself highly reinforcing regardless of sex, and, in male rats can robustly outcompete fentanyl. In contrast, in females, fentanyl intake is relatively insensitive to competing opportunities for optoactivation, except when opportunities to obtain drug or optoactivation are sparse.

neuroscience↗