DNA Methylation Modulation in Aged Rats

Aged rats received a subcutaneous injection of saline (0.9% NaCl) or methionine (200 mg/kg; Sigma-Aldrich, St. Louis, Missouri, USA) twice a day (12-h interval) for 30 days. This dosage was previously shown to induce global DNA hypermethylation [23 (link)]. For the RG108 experiment, bilaterally cannulated young rats (ACSF-SHAM: n=12; ACSF-DBS: n=12; RG108-SHAM: n=14; RG108-DBS: n=12) were infused with either RG108 (Axon Medchem) or artificial cerebral spinal fluid (ACSF) for 30 days at a dosage previously shown to reduce DNA methylation [24 (link)]. RG108 in 20% DMSO was diluted to 200 ng/µL in ACSF. Drugs (2 µL) were infused into the dHPC using a Hamilton syringe connected to the internal cannula through polyethylene tubing (Protech international, Texas, USA) at a rate of 0.5 µL/min over 4 min. The internal cannula was left inside the guide cannula for an additional 3 min to ensure proper diffusion of the infused drug.