Changes in exploratory behaviour of hamsters following treatment with 8-hydroxy-2-(di-n-propylamino)tetralin.

ABSTRACT

The influence of the centrally active 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on the exploration of objects was studied in hamsters, using a radioactographic method. This spatial paradigm allows the study of the behavioural expression of underlying locomotor and cognitive (attentional, mnemonic, representative) mechanisms. The drug was found to enhance the cognitive components of the exploratory process, i.e. object-oriented exploration, habituation and, under certain temporal conditions, response-to-change, in a dose-dependent manner. Since drug-injected animals did not differ from controls when no object was present, 8-OH-DPAT probably has no role in non-oriented exploratory activity. The influence of time was further investigated by varying the duration of successive trials and intertrial intervals. In situations where the durations were extremely shortened (3-min trials/3-min intertrial intervals), drug-treated subjects, in contrast to control ones, exhibited a 'hypernormal' time course they explored and habituated. 8-OH-DPAT appears to increase the efficiency of exploration possibly via a positive effect on arousal or attention. 8-OH-DPAT is assumed to act on 5-HT somatodendritic autoreceptors, lowering 5-HT utilization in the hippocampus, which is the main structure implicated in spatial memory. This exploration paradigm could be employed in the study of time components of environmental adaptation without the need to restrain subjects.