PRELIMINARY COMMUNICATION CHANGES IN THE EXPRESSION OF METABOTROPIC GLUTAMATE RECEPTOR 5 (mGluR5) IN THE RAT HIPPOCAMPUS IN AN ANIMAL MODEL OF DEPRESSION Joanna M. Wieroñska , Piotr Brañski , Bernadeta Szewczyk , Agnieszka Pa³ucha , Mariusz Papp , Piotr Gruca , El¿bieta Moryl , Andrzej Pilc Changes in the expression of metabotropic glutamate receptor 5 (mGluR5) in the rat hippocampus in an animal model of depression. J.M. WIEROÑSKA, P. BRAÑSKI, B. SZEWCZYK, A. PA£UCHA, M. PAPP, P. GRUCA, E. MORYL, A. PILC. Pol. J. Pharmacol., 2001, 53, 659–662. The aim of our study was to investigate the level of metabotropic glutamate receptors (mGluRs) in the brains of rats after chronic mild stress. Using Western blotting procedure we showed that the level of mGluR5 receptor protein was increased in CA1 and de- creased in CA3 region of the hippocampus. Our results indicate that mGluR5 can possi- bly be engaged in the mechanism of depression. Key words: chronic mild stress, hippocampus, metabotropic glutamate receptors Abbreviations: ACPC – 1-aminocyclopropane- carboxylic acid, CMS – chronic mild stress, 5,7-DCKA – 5,7-dichlorokynurenic acid, DG – dentate gyrus, mGluR – metabotropic glutamate receptor, MK-801 – (5R,10S)-(+)-5-methyl-10,11- -dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine, MPEP – 2-methyl-6-(phenylethynyl)-pyridine, NMDA – N-methyl-D-aspartic acid, SDS – sodium dodecyl sulphate, TBS – Tris-buffered saline Glutamate is the main excitatory neurotransmit- ter in the brain [5]. It interacts with two kinds of receptors, the ionotropic and the metabotropic glu- tamate receptors (mGluRs). The latter are a rela- tively new group of receptors identified in the last years. Receptors belonging to this group are coupled with G-proteins and comprise eight receptor types (mGluR1-8) which have been clasified into three groups according to their sequence homology, effec-