Electrophysiological differences between the shell and core of the rat nucleus accumbens were investigated by intracellular recordings from an in vitro slice preparation. The average input resistance of neurons recorded in the shell was larger than in the core. Neurons in the core were characterized by a more negative resting membrane potential than neurons in the shell. Furthermore, bath-applied dopamine attenuated synaptic responses recorded in the shell, but not in the core. Thus, the two main subregions of the nucleus accumbens differ both in basal membrane properties and in dopaminergic modulation of synaptic transmission.