Immunohistochemistry showed immunoreactive staining of Npas4 in the hippocampi (a) and adjacent cortices (b) of the normal control rat brains.

<p>Immunohistochemistry of Npas4 showed strong immunoreactive staining in the hippocampus (c) and adjacent cortex (d) at 72 h after kindling. The black arrowheads indicate Npas4-positive cells. (e) A comparison of the mean OD value between the epileptic and normal rats. The mean OD value indicated that Npas4 expression in the hippocampi of the rats increased at 6 h after the pilocarpine-induced seizure. The highest level of Npas4 expression occurred at 24 h and then began to decline, reaching its lowest level at 30 d. The Npas4 expression levels differed significantly between normal and epileptic rats between 6 h and 30 d after kindling (*P<0.05). (f) A comparison of the mean OD values between epileptic and normal rats. The mean OD value indicated that Npas4 expression in the adjacent cortices of the rats increased at 24 h after pilocarpine-induced seizure and reached its highest level at 72 h. The lowest level of Npas4 expression occurred at 60 d. There were significant differences in Npas4 expression levels between the normal and epileptic rats from 6 h to 60 d after kindling (*P<0.05).