Phlorizin, a competitive inhibitor of glucose transport, facilitates memory storage in mice

Posttraining intraperitoneal administration of phlorizin (3.0-300.0 mu g/kg), a competitive inhibitor of glucose transport from blood to brain, facilitated 48-h retention, in male Swiss mice, of a one-trial step-through inhibitory avoidance task. The dose-response curve was an inverted-U shape. Phlorizin did not increase the retention latencies of mice that had not received a foot shock during training. The effects of phlorizin (30.0 mu g/kg) on retention were time dependent, and the administration of phlorizin (30.0 mu g/kg) 5 or 10 min prior to the retention test did not affect the retention performance of mice given posttraining injections of saline or phlorizin (30.0 mu g/kg). These findings indicate that phlorizin influenced memory storage, but not memory retrieval. Finally, the simultaneous administration of phlorizin (3.0-300.0 mu g/kg, ip) antagonized, in a dose-related manner, the memory impairment induced by insulin (8 IU/kg, ip). Taken together, the results show that phlorizin enhance retention acting as a '"glucose-like substance" although the mechanism(s) of this enhancement is unknown. (C) 1999 Academic Press.