Gene expression in prefrontal cortex and hippocampus during an operant conditioning task

RAPANELLI M; FRICK LUCIANA ROMINA; ZANUTTO BS

Chicago, IL, USA

Congreso; 39th annual meeting of the Society for Neuroscience (SfN); 2009

Society for Neuroscience (SfN)

We studied the expression of immediate early and plasticity-related genes in the prefrontal cortex (PFC) and Hippocampus (Hipp) while animals are learning an operant conditioning task. To study the temporal course of these events, adult rats were divided in five experimental groups: Control (C, animals never leaves bioterium, n=6), Incompletely Trained (IT, 50-65% of responses n=6), Box Control IT (BCIT, animals spent the same time in box as IT n=6), Trained (Tr, 100% of responses and a latency time below 5 s for three consecutive sessions n=6) and Box Control Tr (BCIT, animals spent the same time in box as Tr n=6). Then, we evaluated mRNA expression levels of cAMP Response Element Binding Protein (CREB), Brain-Derived Neurotrophic Factor (BDNF), Synapsin I, Calcium/Calmodulin-dependent protein Kinase II (CaMKII), c-fos, c-jun and Arc using Real-Time RT-PCR. BDNF, CREB, Synapsin I, Arc, c-fos and c-jun expression levels were increased in PFC and Hipp of IT animals compared to BCIT. In the case of CamKII elevated mRNA levels were observed in IT vs BCIT and Tr vs BCTr in the PFC, but no significant differences were observed between experimental groups for this gene. On the other hand, BDNF, CREB, Synapsin I, c-fos, c-jun and Arc begin to decline in Tr vs. BCTr in PFC and HIPP. But, in Synapsin I the levels of Tr returned to BCTr levels. In the case of CamKII, no significant differences were found between groups in the HIPP, however, in PFC we observed elevated levels when we compared Tr vs BCTr and IT vs BCIT. Our results show that increased expression of immediate early and plasticity-related genes is higher during learning than once the task is learned. In this way during learning there is more synaptic plasticity activity than once the neural circuit involved in the new learning is established. Here, we showed the dynamics of gene expression during learning an operant conditioning task for the PFC and HIPP, these changes in mRNA levels involves the HIPP in learning rules and not only to the spatial component of the operant conditioning.