AGS-induced expression of Narp is concomitant with expression of AMPA receptor subunits GluR1 and GluR2 in hippocampus but not inferior colliculus of P77PMC rats

To explore mechanisms of epileptogenesis in audiogenic seizures (AGS), we examined the expression of α-amino-3-hydroxy-5-methyl-4- isoxazoleopropionic acid (AMPA) receptor subunits GluR1 and GluR2 and of the GluR-associated protein Narp in the hippocampus and the inferior colliculus (IC) from AGS-susceptible P77PMC rats after a single AGS and audiogenic kindling. Western blotting and immunohistochemistry showed that Narp was rapidly induced in both the hippocampus and the IC by AGS. In the hippocampus, up-regulation of Narp was concomitant with GluR1 and GluR2 under both conditions of a single AGS and AGS kindling. In the IC, however, Narp was up-regulated, GluR2 down-regulated, and GluR1 unchanged after kindling. In comparison with kindling, neither GluR1 nor GluR2 was changed, while Narp significantly increased in the IC following a single AGS. These findings suggest that down-regulation of AMPA receptor GluR2 subunit in the IC may contribute to AGS-mediated epileptogenesis, and up-regulation of Narp in the IC may be involved in audiogenic seizures.