Conditioning training and retrieval increase phospholipase A2 activity in the cerebral cortex of rats

In rats, phospholipase A₂ (PLA₂) activity was found to be increased in the hippocampus immediately after training and retrieval of a contextual fear conditioning paradigm (step-down inhibitory avoidance [IA] task). In the present study we investigated whether PLA₂ is also activated in the cerebral cortex of rats in association with contextual fear learning and retrieval. We observed that IA training induces a rapid (immediately after training) and long-lasting (3 h after training) activation of PLA₂ in both frontal and parietal cortices. However, immediately after retrieval (measured 24 h after training), PLA₂ activity was increased just in the parietal cortex. These findings suggest that PLA₂ activity is differentially required in the frontal and parietal cortices for the mechanisms of contextual learning and retrieval. Because reduced brain PLA₂ activity has been reported in Alzheimer disease, our results suggest that stimulation of PLA₂ activity may offer new treatment strategies for this disease.