Requirement of hippocampal phospholipase A2 activity for long-term memory retrieval in rats

Summary. In rats, the inhibition of phospholipase A₂ (PLA₂) in hippocampus was reported to impair memory acquisition. In the present study we investigated in rats whether PLA₂ inhibition in hippocampus is also related to impairment of memory retrieval. Rats were bilaterally implanted with cannulae in hippocampal CA1 region. After recovery, animals were submitted to one-trial step-down inhibitory avoidance task and tested for long-term memory (LTM) 24 h later. Before test session, animals received infusions of vehicle or the PLA₂ inhibitor PACOCF₃. Inhibition of PLA₂ activity impaired LTM retrieval. Memory impairment was fully reversed once PLA₂ activity was recovered. Moreover, LTM retrieval per se increased PLA₂ activity. To our knowledge, we demonstrated for the first time that PLA₂ activity is required for memory retrieval. Because reduced PLA₂ activity has been found in Alzheimer’s disease brains, the present results may be relevant to clarify at least part of the biology of this disorder.