Fig. 2. C/EBPβ and -δ mRNA levels after inhibitory avoidance training. Northern blot analyses were performed of hippocampal extracts taken from rats immediately (0 h), 3, 6, 9, 20, and 72 hr, and 1 week after training. A, Two independent autoradiographs show mRNA levels of individual animals that (1) underwent full training (+), (2) entered the IA apparatus but received no shock (−), or (3) received the shock without exposure to the apparatus [shock only (SO)]. Cyclophilin was used as a control probe for normalization of both C/EBP hybridizations.B, Densitometric analysis of C/EBPβ autoradiographs described in A. Trained animals showed a significant induction of C/EBPβ mRNA at 9 hr (p < 0.01) and 20 hr (p < 0.01) compared with control rats immediately killed after training (0 h −). In contrast, no significant changes in C/EBPβ were found in any of the control no shock or shock only groups. Data are expressed as mean percentage ± SEM of the 0 h − (100%) control mean values. C, Densitometric analysis of C/EBPδ Northern blots described in A. C/EBPδ mRNA is significantly induced in rats 20 hr (p < 0.01) after training compared with 0 h − control levels. No significant changes were detected in any of the controls groups. Data are expressed as mean percentage ± SEM of the0 h − (100%) control mean values.