Mesial temporal lobe epilepsy (mTLE) in human can be reproduced by a unilateral injection of kainic acid (KA) into the dorsal hippocampus in a mouse model of mTLE. To identify subtle anatomical and functional changes, we performed immunohistochemical and electrophysiological investigations in the hippocampus 3-4 weeks following KA-injection. Coronal slices obtained from dorsal, middle and ventral hippocampus were prepared from adult mice. To induce network oscillations bath application of low concentration of KA (400 nM) was used. Indirect immunofluorescent labeling for neurochemical markers of glial cells (GFAP), neurons (NeuN) and various sets of interneurons were performed on slices from control and epileptic animals. Immunohistochemical analyses revealed a dramatic loss of interneuronal markers including GAD-67 in all areas and layers of the hippocampus. Field recordings in control animals detected both theta and gamma population rhythms. In contrast, in coronal slices from KA-treated animals it was possible to elicit persistent gamma but not theta rhythms. These results indicate the existence of structural and functional alterations in the hippocampus in this mouse model of mTLE. These alterations primarily influence GABAergic interneurons and affect the generation of network oscillations at theta and gamma frequencies.