**2.5. Immunohistochemistry**

Free-floating sections were pretreated for 20 min with 3 % hydrogen peroxide in PBS to quench endogenous peroxidase. They were then washed with PBS (3 x 10 min), preincubated for 90 min at room temperature in PBS containing 0.05 %. Triton X-100 and 3 % normal horse serum. Sections were incubated for 36 h at 4 °C with Mouse anti-AVP antibody (1: 5000 dilution).

After incubation, sections were rinsed extensively with PBS (four times, 15 min) and incubated for 1.5 h in a 1/100 dilution of biotin conjugated horse anti-goat antibody and other secondary antibodies. Texas Red conjugated rabbit anti-mouse antibody (1/200; dilution; Jackson ImmunoResearch). For amplification, we used tyramide signal amplification fluorescence system technology (NEN, Boston, MA, USA). For details see Banisadr et al. [36]. After washing, sections were mounted onto gelatin-coated slides in Vectashield (Vector) and observed on fluorescent microscope (BX61; Olympus, Melville, NY) and a connected image-acquisition software (Analysis) was used.
