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

N⁶ -methyladenosine (m⁶ A) plays a crucial role in regulating neuroplasticity and different brain functions at the posttranscriptional level. However, it remains unknown whether m⁶ A modification is involved in acute and chronic morphine exposure.

In this study, we conducted a direct comparison of m⁶ A levels and mRNA expression of m⁶ A-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 m⁶ A modification levels, we employed the m⁶ A dot blot assay, while mRNA levels of m⁶ A-associated proteins were measured using a quantitative polymerase chain reaction (qPCR) assay. These analyses were performed to investigate whether and how m⁶ A modification and m⁶ A-associated protein expression will change following morphine exposure.

The overall m⁶ A methylation and mRNA levels of m⁶ A-associated proteins were not significantly altered in brain regions that were either activated or not activated during acute morphine stimulation. Similarly, the overall m⁶ A modification and mRNA levels of m⁶ A-associated proteins remained unaffected in several key brain regions associated with reward following chronic morphine exposure.

This study showed that the overall m⁶ A modification level and mRNA expression levels of m⁶ A-associated factors were not affected after acute and chronic morphine exposure in different brain regions, indicating m⁶ A modification may not be involved in brain response to morphine exposure.