Intracerebroventricular (i.c.v.) injection of rat corticotropin-releasing factor (rCRF) at doses of 5-20 micrograms in rats induces epileptogenic activity characterized by pacemaker-like spikes localized in the hippocampal leads. Such an effect was still present in rats neonatally treated with saline but was absent in those neonatally treated with monosodium glutamate (MSG), a treatment that caused marked changes in the concentration of several brain neurotransmitters and neuropeptides in hypothalamic nuclei where CRF is highly concentrated and is believed to induce endocrinologic and behavioral effects. The present results suggest the rCRF-induced spiking activity is mediated by activation of neuronal pathways sensitive to MSG neurotoxic effect.