OBJECTIVE: The aim of this study was to evaluate the effects of acute administration of zolpidem (Zolp) on mice's habituation response to the open-field (OF) apparatus, a model of non-associative memory.
METHODS: Three-month old male Swiss mice were assigned to one of the following groups: Sal/HC, Sal/OF and Zolp/OF. Mice received an intraperitoneal (i.p. ) saline (Sal) injection and, 30 minutes later, they were returned to home cage (HC) (Sal/HC group) or exposed to the OF arena (Sal/OF). Still, a group of mice received an i.p. 10 mg/kg Zolp injection and 30 minutes later were exposed to OF. Animals were exposed to OF for 10 minutes and their general activity was quantified in the first 3 minutes. Ten days after the first exposure, all animals were submitted to a 3-minute OF exposure and their general activity was quantified.
RESULTS: In the first exposure, the Zolp/OF group presented a decreased peripheral, central and total locomotion frequencies and increased immobility duration in relation to the Sal/OF group. In the second exposure, only the Sal/OF group presented habituation behavior, demonstrated by a significant decrement of central and total locomotion frequencies and increased immobility duration when compared to Sal/HC group (exposed for the first time to OF). Conversely, Zolp/OF group did not differ from the Sal/HC group in any of the parameters analyzed, suggesting habituation impairment.
CONCLUSION: Our results suggest that the acute administration of 10 mg/kg Zolp before the first exposure to OF promotes a reduction on motor activity and induces habituation deficits, reflecting a non-associative memory impairment.
Keywords: sleep; memory/drug effects; memory/physiology; locomotion; motor activity; pyridines/administration & dosage; hypnotics and sedatives/pharmacology; rats.