No significant change of N⁶‐methyladenosine modification landscape in mouse brain after morphine exposure

Abstract

ObjectivesN6‐methyladenosine (m6A) plays a crucial role in regulating neuroplasticity and different brain functions at the posttranscriptional level. However, it remains unknown whether m6A modification is involved in acute and chronic morphine exposure.Materials and methodsIn this study, we conducted a direct comparison of m6A levels and mRNA expression of m6A‐associated factors between morphine‐treated and nontreated C57BL/6 wild‐type mice. We established animal models of both acute and chronic morphine treatment and confirmed the rewarding effects of chronic morphine treatment using the conditioned place preference (CPP) assay. The activation status of different brain regions in response to morphine was assessed by c‐fos staining. To assess overall m6A modification levels, we employed the m6A dot blot assay, while mRNA levels of m6A‐associated proteins were measured using a quantitative polymerase chain reaction (qPCR) assay. These analyses were performed to investigate whether and how m6A modification and m6A‐associated protein expression will change following morphine exposure.ResultsThe overall m6A methylation and mRNA levels of m6A‐associated proteins were not significantly altered in brain regions that were either activated or not activated during acute morphine stimulation. Similarly, the overall m6A modification and mRNA levels of m6A‐associated proteins remained unaffected in several key brain regions associated with reward following chronic morphine exposure.ConclusionThis study showed that the overall m6A modification level and mRNA expression levels of m6A‐associated factors were not affected after acute and chronic morphine exposure in different brain regions, indicating m6A modification may not be involved in brain response to morphine exposure.