Integrative Analysis of Morphine-Induced Differential Circular RNAs and ceRNA Networks in the Medial Prefrontal Cortex.

Circular RNAs (circRNAs) are a novel type of non-coding RNAs. Despite the fact that the functional mechanisms of most circRNAs remain unknown, emerging evidence indicates that circRNAs could sponge microRNAs (miRNAs), bind to RNA binding proteins (RBP), and even be translated into protein. Recent research has demonstrated the crucial roles played by circRNAs in neuropsychiatric disorders. The medial prefrontal cortex (mPFC) is a crucial component of drug reward circuitry and exerts top-down control over cognitive functions. However, there is currently limited knowledge about the correlation between circRNAs and morphine-associated contextual memory in the mPFC. Here, we performed morphine-induced conditioned place preference (CPP) in mice and extracted mPFC tissue for RNA-sequencing. Our study represented the first attempt to identify differentially expressed circRNAs (DEcircRNAs) and mRNAs (DEmRNAs) in the mPFC after morphine-induced CPP. We identified 47 significantly up-regulated DEcircRNAs and 429 significantly up-regulated DEmRNAs, along with 74 significantly down-regulated DEcircRNAs and 391 significantly down-regulated DEmRNAs. Functional analysis revealed that both DEcircRNAs and DEmRNAs were closely associated with neuroplasticity. To further validate the DEcircRNAs, we conducted qRT-PCR, Sanger sequencing, and RNase R digestion assays. Additionally, using an integrated bioinformatics approach, we constructed ceRNA networks and identified critical circRNA/miRNA/mRNA axes that contributed to the development of morphine-associated contextual memory. In summary, our study provided novel insights into the role of circRNAs in drug-related memory, specifically from the perspective of ceRNAs.