To explore the mechanism of interleukin-1beta (IL-1β) in the onset of seizure and the effect of IL-1β on the expression of adenylyl cyclase (AC) in rats with seizure induced by L-glutamate. Experimental rats were first injected with IL-1β and then L-glutamate (a dose under the threshold) was injected into the right lateral ventricle. The rats were sacrificed 4 h after the onset of epileptic activity and examined for changes in behavior, immunohistochemistry and compared with those with seizure induced by L-glutamate alone. It was found that the expression of AC in hippocampal and neocortex of rats with seizure induced by IL-1β and L-glutamate were stronger than that of control group (P＜0.05), without significant difference found between the L-glutamate group and IL-1β plus L-glutamate group in the expression of AC, the latent period and the severity of seizure. When IL-ra were given (i. c. v. ) first, there was no epileptic activity and the expression of AC did not increase. There were no differences in the expression of AC of rats with IL-1ra and that of control rats. But when 2-methyl-2-(carboxycyclopropyl)glycine (MCCG) was given (i. c.v. ) first, the strongest expression of AC, the shortest latent period and the the most serious seizure activities were observed. The results indicated that IL-1β could facilitate the onset of epilepsy induced by L-glutamate through IL-1R, metabotropic glutamate receptors might work with IL-1R and the increased expression of AC might be involved in the process.