Abstract: Two instrumental enzymes, Chymotrypsin (CT) and Trypsin (T), both are pro-teolytic enzymes capable of destroying some bonds of proteins and peptides, were usedin this experiment. A total of 26 young adu1t male albino rats served as the threenon-consolidation groups (NC) of DBA memory: normal saline solution (NS/NC),Trypsin (T/NC) and Chymotrypsin (CT/NC). After bilateral injection of CT and T into the Hippocampus (iH: AP_2L_2H_4 andAP_4L_3H_5), different effects were observed on the conditioned reflex of DBA memorymodel (CR_(DBA)). 72 hours after iH. T, retention of CR_(DBA) clearly decreased, but afteriH. CT, memory remains consolidated. Differences in successive number of CR_(DBA)(SN_(CR)) and rate of CR_(DBA) (CR%) were statistically significant. The experimentaldoses of iH. T and CT approximately equal 1/3 of their LD_(50).

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