Opioid-Induced Regulation of Cortical Circular-_011731 Is Associated with Regulation of Sponge Target .

Opioid use induces neurobiological adaptations throughout mesolimbic brain regions, such as the orbitofrontal cortex (OFC), which mediates decision-making and emotional-cognitive regulation. Previously, we showed that a circular RNA (circRNA) species, rno__011731 (), is upregulated in the OFC of rats following chronic self-administration (SA) of the opioid heroin. is derived from , which encodes the regulatory subunit of the glutamate ionotropic NMDA receptor, GluN2B. However, the upstream regulatory mechanisms of biogenesis and the downstream consequences of dysregulation remain unknown. We hypothesized that opioid-induced elevation of is accompanied by regulation of circRNA biogenesis enzymes, and that may sponge microRNAs (miRNAs), as miRNA sponging is a well-described characteristic of circRNAs. To test these hypotheses, we established an in vitro primary cortical cell culture model to examine alterations in expression following exposure to the opioid morphine. We measured mRNA expression of known circRNA splicing factors and observed significant downregulation of Fused in Sarcoma (), a negative regulator of circRNA biogenesis, following 90 min or 24 h of morphine exposure. Downregulation of at 24 h post-morphine was accompanied by upregulation of and downregulation of , a predicted miRNA target of . Luciferase reporter assays confirmed interaction of with . Finally, we report a significant negative relationship between and expression in the OFC of rats following heroin SA. We conclude that regulation of is an opioid-induced neuroadaptation that may impact downstream signaling of miRNA pathways in the frontal cortex.