Isolation and Preparation of Hippocampal Slices

To obtain hippocampal slices, the mice were decapitated between 9:00 a.m. and 12:00 a.m. under isofluorane anesthesia; the brains were removed from the skulls, and the hippocampi were isolated. With the use of a tissue chopper (McIlwain), both hippocampi were cut to obtain transverse slices (300 µm). The slices were then incubated for at least 1 h in artificial cerebrospinal fluid (ACSF) containing (in mM): 126 NaCl, 3.5 KCl, 1.2 NaH₂PO₄, 1.2 MgCl₂, 2 CaCl₂, 25 NaHCO₃, and 11 glucose (pH 7.3) saturated with 95% O₂ and 5% CO₂. The slices were treated for 20 min with CGS 21680, 300 nM or for 10 min with DHPG 100 µM. ZM 241385 (500 nM) and MPEP (10 µM) were added 15 min before and then kept throughout the application of CGS 21680 or DHPG. The concentrations of A_2AR ligands were chosen on the basis of a previous paper in which these concentrations proved to be effective in modulating STEP activity [16 (link)]. As for the mGlu₅R ligands, we obtained the concentrations from the literature [24 (link),27 (link)].