From dysregulated microRNAs to structural alterations in the striatal region of METH-injected rats.

Methamphetamine (METH) is a high addictive psychostimulant drug which triggers brain atrophy via neuronal degeneration. Striatum is the main part of the brain that is regarded as a key target for drug-induced damages. MiRNAs as small regulatory molecules at the post-transcriptional level play a major role in biological pathways. In this study, initially we performed behavioral assessment in METH-treated rats. Then, we examined striatal volume and dendritic length, and also the levels of tyrosine hydroxylase (TH), caspase-3 and glial fibrillary acidic protein (GFAP) were immunohistochemically assessed. Moreover, we investigated miRNA expression profiling using high-throughput small RNA-seq technology. Based on our data, METH provoked declined motor coordination, decreases in striatal volume and dendritic length along with over-activation of astrogliosis. In addition, METH treatment down-regulated TH level while it induced up-regulation of caspase-3 in the striatal region. Furthermore, according to miR-seq analysis, we found 167 deregulated miRNAs in the striatum upon METH treatment, that among them rno-let-7b-5p, rno-miR-485-5p, rno-miR-326-3p, rno-miR-34a-5p, rno-miR-3068-5p showed high miRNA-target gene interaction. Pathway analysis revealed that miRNAs and their target genes may be involved in cell apoptosis, growth, differentiation as well as synaptic plasticity associated pathways. Altogether, we can conclude that METH noticeably elicited neuro-degeneration in the dorsal striatum.