**2.4. Tissue preparation**

*Meriones* were anesthetized with sodium pentobarbital (70 mg/kg, i.p; Sanofi, Libourne,France) and perfused transcardially with heparin in physiological saline, followed by 500 mL of a freshly prepared solution of 4 % (wt / vol) paraformaldehyde in phosphate – buffered saline (PBS ; pH = 7.4). The brains were rapidly removed and postfixed overnight in 4 % paraformaldehyde at 4 °C. Forty micrometer thick coronal sections were cut with a Vibratome (VT 1000S; Leica, Nussloch, Germany). Brain sections were collected in cold PBS.
