Three incremental doses of recombinant alpha-interferon (IF) were applied iontophoretically to hippocampal and hypothalamic cells. IF produced a dose-dependent long-lasting excitation in hippocampal neurons, whereas, in the hypothalamus alpha-IF elicited biphasic responses. The highest IF currents induced changes in the amplitude of the action potentials on both structures. Our observations suggest that IF could have a selective effect on the specific areas studied.