4.3. Stimulation Protocol

The stimulation electrode (anode, diameter 2.1 mm; DIXI Medical, Besançon, France) was screwed into the electrode holder filled with a saline solution (0.9% NaCl). A custom-made restraining box was used to hold a larger rectangular rubber-plate electrode (cathode, 9.5 cm²; Physiomed Elektromedizin AG, Schnaittach, Germany; Figure 5E,F) against the ventral thorax, as previously described [29]. The animals were stimulated for five consecutive days (2 × 20 min/day; 5 h interstimulation interval [29,30,32]; linear fade-in and fade-out; 10 s ramp [27]), with an anodal constant current (0.2 mA) using a DC-Stimulator Plus (NeuroConn, Illmenau, Germany) or an Open-tES stimulator specifically designed for rodent research [31]. The control (Sham) animals were subjected to the same procedure (surgery, restraining box, and electrode fixation) but no current was delivered.