Multisession epidural direct current stimulation of the auditory cortex mitigates age-related transcriptomic dysregulation in Wistar rats

Abstract

[EN]Age-related hearing loss (ARHL) disrupts ascending auditory inputs, impairing auditory signal transmission, triggering cortical hyperexcitability, and increasing the risk of age-related cognitive decline. In early aging, multisession epidural direct current stimulation (DCS) of the auditory cortex (AC) preserves auditory thresholds and prevents cortical hyperexcitability in Wistar rats. Here, we hypothesized that multisession DCS could halt transcriptional dysregulation in the AC at the earliest stages of aging. We have characterized age-related transcriptional changes in the AC to assess DCS-mediated effects by RNA-seq. At 18.13 months, non-stimulated, aged rats (NES) showed 194 differentially expressed genes (DEGs) in relation to young controls (YG), with enrichment in pathways associated with GABAergic, glutamatergic, and dopaminergic synapses, long-term potentiation/depression, inflammaging, autophagy, apoptosis and neurodegeneration. The upregulated genes included Gabrb1, Grin2b, Rac3c, Tnr, and Ndst1, suggesting compensatory hyperactivity, excitatory/inhibitory imbalance, and stiffening of perineuronal nets (PNN) around parvalbumin (PV) interneurons. Electrically stimulated (ES) rats showed 86 DEGs in relation to YG, with no significant enrichment in aging-related pathways. By contrast, NES vs ES showed 1393 DEGs, with strong enrichment in aging-related pathways. Also, many of the 121 common DEGs across comparisons, which are upregulated in NES and downregulated in ES, are related to neurotransmission (Gabrb1, Grin2b), synaptic scaffolding (Dlg2, Prkca), trophic signaling (Ntrk2, Igf1r) and PNN (Tnr, Ndst1). Based on these findings, multisession DCS curbs maladaptive genomic reprogramming in the aged AC most likely by preserving excitatory/inhibitory balance and maintaining PNN integrity, thereby protecting the AC from ARHL and cognitive vulnerability.