Functional imbalances between excitatory and inhibitory synaptic function have been suggested to occur in Alzheimer’s disease (AD). AD and fronto-temporal dementia (FTD) are the most common forms of tauopathy, consisting in the progressive, intracellular accumulation of pathogenic species of protein tau, leading to altered neuronal function and neurodegeneration. Our investigation focused on the effects of progressive tauopathy on the electrical membrane properties of two subpopulations of hippocampal inhibitory interneurons: Oriens-Lacunosum moleculare cells (OLMs) and Neurogliaform cells (NGFs). We performed single-cell patch-clamp recordings in coronal hippocampal sections obtained from 2, 4, 8 or 12 month-old rTg4510 (a transgenic mouse model of human, familial FTD, carrying the P301L variant of the tau gene) and age-matched WT littermate controls. We measured both electrotonic and electrogenic membrane properties. OLM interneurons in rTg4510 mice showed decreased action potential (AP) peak and hyperexcitability, in the form of increased input resistance -Ri- and AP firing rates. NGFs showed bigger and smaller capacitance, mirrored by lower and higher firing outputs, at 2 and 12 months, respectively; no changes were observed at 4 and 8 months. Our data may represent a tool to provide a single-cell correlate to the progression of AD- and FTD-related alterations of network activity and cognitive performance: to test the causal relationship between single-cell and network altered function in hippocampal CA1, we are currently performing in silico modelling based on these experimental data. This approach can provide an important platform for the development of novel therapeutic strategies, based on the modulation of single neuron activity.