Central gonadotropin-releasing hormone (GnRH) injected intraventricularly (IVT) has been shown to facilitate rat sexual behavior. To elucidate the brain mechanisms of GnRH action, we have applied GnRH to hippocampal brain slices in vitro. Using intracellular recording from 40 hippocampal CA1 pyramidal neurons, we have found GnRH to elicit predominantly excitation. There are two types of excitatory responses. One is a short-latency, short-duration response and the second a long-latency, long-duration response. These responses were characteristic of GnRH and not peptides generally because angiotensin II, which also had an excitatory effect, had only long-latency, short-duration effects. The neural response to GnRH may be involved in the initiation of the behavioral response since the termination of the long-duration response coincides with the onset of the behavior.