After delivering the RF energy, prefilled 1-ml syringes of filler were connected to the end of the needle electrode. Next, a 0.1 ml mixture of filler (HA 23 mg/ml, Glytone 3; Pierre Fabre, Castres, France) and dye (fast green FCF; Sigma-Aldrich) was intradermally injected into the shaved backs of the animals.