Expression of transcription factor ZENK (zif/268) in telencephalon of quail chicks after induced seizure and passive avoidance training

Abstract

Functional significance of an immediate early gene ZENK (zif/268) was examined in telencephalic regions (homologues of neocortex and basal ganglia) of newly-hatched quail chicks; hyperstriatum accessorium (HA), hyperstriatum ventrale (HV), neostriatum (N) and lobus parolfactorius (LPO). Chicks were trained by a green bead soaked either in a strong aversant (methylanthranilate, MeA), in a weak aversant (MeA diluted by ethanol, 1/3MeA), or in water. Chicks were then tested at 45-50 min post-training, and immediately processed for ZENK immunostaining. Neither the training condition (MeA, 1/3MeA, or water) nor the responses at test (recall or amnesia) significantly contributed to the immunopositive cell densities in all of these regions. On the other hand, single intraperitoneal injection of metrazole (CNS convulsant) induced a transient epileptiform seizure, and caused significantly enhanced ZENK expression in HV and LPO but not in HA and N. However, the metrazol-induced seizure did not interfere with the following passive avoidance training, and chicks successfully learned to avoid the aversive bead when tested at 24 hr subsequently. Among three groups of chicks (metrazol-treated, saline control, and untreated chicks), no significant differences were found in their responses at test (recall, generalized avoidance, or amnesia). These results suggest that enhanced ZENK expression may represent lasting neural activities, but may not be involved specifically in the passive avoidance memory formation.