Dissociation of anxiolytic and amnesic effects in the elevated T-maze

Abstract

Benzodiazepines administration produces amnesic and anxiolytic effects. The non-benzodiazepine anxiolytics, like buspirone (BU), seems to have low amnesic effects, but the results obtained vary with the procedures used to evaluate these effects. The elevated T-maze (ETM) is a procedure that allows evaluating both, the amnesic and anxiolytic effects. In the present study, we examined the effect of the administration of a cholinergic antagonist, scopolamine (SC), a classical amnesic agent, and two anxiolytics, diazepam (DZ) and BU in the ETM. Male Wistar rats (200-250 g) were tested in the ETM during 5 min after one of the following treatments: SC (0.5, 1, 3 mg/kg, DZ (2, 5 mg/kg), BU (2, 5 mg/kg) or saline (SAL). In training day each subject was injected and placed in the enclosed arm and the time remaining in this arm was registered; two subsequent avoidance trials (AV) were given. After avoidance trials, each subject was placed in the open arm and the latency to escape (ES) was recorded. In the retention test, the AV and ES latencies were recorded 24 hr after without the administration of the drug. Significant impairment was observed for avoidance latencies in acquisition and retention in the SC groups compared with saline; no changes were observed for escape latencies. Similar effects but in a lesser extent were observed for diazepam in acquisition and retention avoidance latencies; an increase in escape latencies was observed suggesting an anxiolytic effect. Buspirone had no effect in acquisition and retention avoidance latencies; in the animals treated with the higher dose of BU an increase in escape latencies was observed in the first day suggesting an anxiolytic effect. Present results suggest that SC has amnesic effects, but no anxiolytics, DZ and BU induced an anxiolytic effect, but only diazepam induced anterograde amnesia, and that these effects could be dissociated using the ETM.