Effects of lysine-vasopressin in an exploratory behaviour test situation

Changes in the exploratory behaviour pattern in rats were studied over a period of eight weeks. Certain characteristics emerged during repeated exposure to the same environment. The activity of "investigating" behaviour increased, while rearing activity decreased. We suggest that these changes reflect habituation by the animal to the test situation. Administration of lysine-vasopressin (LVP; 5.0 micrograms/kg SC) resulted in some alterations of the exploratory behaviour pattern, but no other behaviours than those observed without drug treatment were seen. The administration of LVP resulted in a higher performance of "investigating" behaviour. Since the change in the exploratory behaviour pattern after LVP administration was similar to that during repeated exposure to the test situation, we conclude that the LVP treatment influenced processes of habituation.