INHIBITORY AVOIDANCE-LEARNING INHIBITS ECTONUCLEOTIDASES ACTIVITIES IN HIPPOCAMPAL SYNAPTOSOMES OF ADULT RATS

Several lines of evidence indicate that ATP may play an important role in Long-Term Potentiation. In this investigation we evaluated the eff ect of a memory task (step-down inhibitory avoidance) on the synaptoso mal ecto-enzymes (ATP diphosphohydrolase and 5'-nucleotidase) involved in the degradation of ATP to adenosine. After the training session, a decrease in the ATPase (40%) and ADPase (29%) activities of ATP dipho sphohydrolase as well as was a decrease in 5'-nucleotidase activity (3 1%) was observed in hippocampal synaptosomes of rats trained and kille d immediately after training. In synaptosomes of rats killed 30 minute s after training, a decrease in ATPase activity (28%) was observed. In the test session, no significant changes were observed in the enzyme activities studied. These results provide new information about the ac tivity of ecto-enzymes involved in nucleotide degradation and their po ssible participation in mechanisms of acquisition and modulation of me mory processing.