Consummatory successive negative and anticipatory contrast effects in inbred Roman rats.

Three experiments were designed to study the performance of female inbred Roman High-(RHA-I) and Low-(RLA-I) Avoidance rats in a consummatory task in which successive negative (cSNC) and anticipatory contrast (cANC) effects were induced by changing the concentration of the sucrose solution used as reward. Both RHA-I and RLA-I rats showed a significant suppression of drinking (cSNC) when they were exposed to 32% sucrose in preshift phase and 4% in postshift phase, in comparison to RHA-I and RLA-I control groups always exposed to 4% sucrose (Experiment 1). By contrast, when the preshift-postshift reward discrepancy was reduced from 32-4 to 22-4 in Experiment 2, both strains showed a suppression of fluid intake on the first postshift trial, whereas only the more emotional RLA-I strain maintained this suppression on subsequent days. Finally, no consumption differences were observed between RHA-I and RLA-I rats exposed to brief daily access to 4% sucrose followed by access to 22% sucrose (cANC, Experiment 3). These results suggest that differences between the Roman rat strains in consummatory contrast paradigms can only be observed when the sucrose solution manipulation implies an incentive loss-attenuated emotional situation, but not when it occurs in an anticipatory manner.