Response of dorsal root ganglion tissue to chronically stimulated electrodes

Abstract

Peripheral sites including the dorsal root ganglion (DRG) are target implantation regions for neural prosthetics that restore function/provide therapy. To improve long‐term performance, conductive polymers and carbon nanotubes (CNTs) can be coated on the electrode surface and doped with anti‐inflammatory drugs. We compared the performance of and tissue damage associated with chronically‐stimulated modified microelectrodes. Following partial laminectomy, uncoated, PEDOT/CNT and dexamethasone‐doped PEDOT/CNT coated dual microelectrodes were implanted into the DRG of thirteen adult male rats. For chronic stimulation, cathodic pulses (20 μAmps, 200 μs) were followed by anodic pulses (10 μAmps, 400 μs) for 1 h/d for 10 of 14 d. Hematoxylin and eosin staining along with the following were used: Iba1 (microglia/macrophages), NF200 (neuronal axons), NeuN (neurons), GFAP (astrocytes), S100 (Schwann cells), vimentin (fibroblasts) and caspase‐3 (cell death). Quantitative image analyses were performed using MATLAB and electrode performance assessed. Our results indicate that coated microelectrodes perform better and cause less tissue damage than uncoated controls suggesting that these coatings may be valuable modifications for in vivo applications. Funding for this work was provided in part by the Department of Defense TATRC grant WB1XWH‐07‐1‐0716 and the National Institute of Health R01NS062019.