Effects of vasopressin, des-glycinamide vasopressin and amphetamine on a combined passive and active avoidance task

The effects of peripherally injected arginine vasopressin (AVP), its des-glycinamide derivative (DGAVP), which has limited pressor activity, and d-amphetamine (AMP) were studied on a combined passive and active avoidance task (Carew 1970). In this procedure, the rat experiences mild foot-shock in one of two distinctively coloured compartments, followed by drug treatment. On the next day, re-entry latency into either of the two compartments is measured (latency index), and the actual compartment chosen is noted (choice index). Both measures were affected by the intensity of the shock. A moderate dose of AVP (25 micrograms/kg) increased latencies, but only when a relatively low shock intensity was used; choice was not markedly affected. DGAVP did not significantly affect performance under any condition. AMP affected latency scores as well as choice behaviour at the lower shock level but, presumably due to "ceiling" effects, did not exert an effect in the high shock condition. The negative DGAVP findings suggest that the behavioural potency of peripherally injected AVP was due to pressor activity, rather than any direct action on cognitive mechanisms. Moreover, this indirect AVP effect on mnemonic performance was relatively weak, since only the latency, but not choice, measure was significantly affected. It is concluded that the Carew paradigm provides a more comprehensive assessment of behaviour than traditional passive or active avoidance procedures.