The present study describes the use of nose-poke habituation as a memory task and demonstrates that it is sensitive to hypo- and hypermnestic pharmacological treatments administered post-trial. Habituation of nose-poke behavior of rats was defined as a reduction in number of nose-pokes compared to baseline. It was measured using a board with 16 holes, to which animals were exposed on 2 consecutive days (baseline and test) for 10 min, respectively. After the first exposure, rats were injected intraperitoneally (i.p.) immediately or with a delay of 2.5 h with doses of
diazepam (0.9-4.5 mg/kg) known to be hypomnestic, or
cholecystokinin (CCK-8S; 0.2-25 micrograms/kg), which was reported to have memory facilitating effects. An enhancement of habituation in comparison with vehicle controls was interpreted in terms of a hypermnestic effect of the treatment. Conversely, hypomnestic action of the
drug treatment was inferred from a reduced habituation. The results show that when
diazepam was injected immediately post-trial, the normal reduction in number of nose-pokes during test was prevented, indicative of a failure to habituate presumably due to an
amnesia for the baseline/training trial. In contrast, enhanced habituation (facilitation of memory) was induced when
CCK-8S was injected immediately post-trial, as reflected by a decrease in number of nose-pokes during test compared to control animals. The effects were not due to enduring proactive effects of the compounds on performance during test, since post-trial
injections of
diazepam or
CCK-8S with a delay of 2.5 h did not have the effects that immediate post-trial injection had.(ABSTRACT TRUNCATED AT 250 WORDS)