Multiple patch clamp recordings represent a powerful tool to investigate functional synaptic connectivity among individual cells. This technical approach is particularly useful to study the synaptic organization of microcircuits in certain brain areas, e.g., the striatum, which are characterized by heterogeneous cell populations and an apparent lack of an anatomically ordered cytoarchitecture. Fast-spiking interneurons (FSIs) represent less than 1 % of striatal neurons, but despite their rareness they exert a strong influence on signal processing by striatal microcircuits and principal cells output. Little is known about the functional properties of chemical and electrical synapses connecting striatal FSIs to each other. Here we describe a simple dual patch clamp approach to investigate electrical and GABAergic synapses in mouse neostriatal slices.