The effects of vasopressin on positively rewarded responding and on locomotor activity in rats.

It has been suggested that arginine-vasopressin (AVP) enhances cognitive, and especially mnemonic, ability. Most studies have employed shock avoidance paradigms; we report the results of a study in which saline or vasopressin (0, 0.5 or 1 microgram, mcg, per rat, subcutaneous) pre-treated rats learned to press a lever for food reward. AVP was found to have a disruptive effect on aquisition, particularly when the tendency for these rats to produce extreme learning scores was taken into account. Locomotor activity, with and without vasopressin pre-treatment (0, 0.5, 1 or 2 mcg/rat), was also studied. Only the highest dose significantly reduced activity; therefore, the effects of AVP on acquisition are unlikely to have been caused by motor disruption. The results are discussed in terms of an hypothesis which suggests that AVP enhances arousal, hence influencing performance.