EVIDENCE FOR THE INVOLVEMENT OF HIPPOCAMPAL CO PRODUCTION IN THE ACQUISITION AND CONSOLIDATION OF INHIBITORY AVOIDANCE-LEARNING

CARBON monoxide (CO), produced through the action of haem oxygenase (H O) isoenzymes, has been recently postulated as a retrograde messenger in the early stages of long-term potentiation (LTP). In the present st udy, rats submitted to an inhibitory avoidance task there is a signifi cant increase (+ 76%) in hippocampal HO activity immediately after tra ining (0 min), but not at 60 min posttraining. No changes were observe d in cerebral cortical and cerebellar HO activity. Bilateral intrahipp ocampal infusion of the HO inhibitor zinc-protoporphyrin-IX (ZnPP) (2 mu g side(-1)) caused full amnesia for inhibitory avoidance when given 10 min before training or immediately after training, but not 60 min after training. These findings provide evidence that CO production in the hippocampus is important for the early stages of memory processing of an inhibitory avoidance training.