Intake suppression due to incentive downshift is not a byproduct of enhanced search behavior

LOPEZ SEAL, F.; CUENYA, L.; SUAREZ, A.; MUSTACA, A.

New Orleans

Congreso; Neuroscience 2012; 2012

Rats shifted from 32% to 4% sucrose solution consume less from the 4% solution than those experiencing the 4% solution only. This consummatory suppression is accompanied by an increase in search behavior, including rearing, nose-down locomotion, ambulation, and the sampling of new sources of reward. As most studies focus on consummatory behavior, this effect is known as the consummatory successive negative contrast (cSNC) effect. The study of the cSNC effect has been very productive, especially with regards to the identification of the brain areas and neurochemichals involved. However, a basic question remains unanswered: Whether the consummatory suppression stems from the active reduction of the intake or is a byproduct of increased search. The main goal of study 1 was to determine if consummatory suppression occurs even when searching is not an option. Rats were trained with either 32% or 4% sucrose solution for ten days in a restrainer that impeded movement. On days 11 through 15, all subjects received the 4% sucrose solution. The downshifted animals showed consummatory suppression relative to the controls. However, stress is known to affect consummatory behavior, and in particular to enhance consummatory suppression. Thus, the goal of study 2 is to assess whether stress induced by restraint affected consumption in study 1. A second goal was to evaluate if the contrast-reducing effect of anxiolytics--a robust feature of the cSNC--would also be present under the unusual situation of restraint. Study 2 was identical to study 1, except that on days 12 and 13, half of the animals in each group received an injection of diazepam(4mg/kg) and the other half received saline. Among the unshifted animals, diazepam and saline treatments yielded similar intakes, suggesting that restraint did not affect consummatory behavior. Further, relative to the saline treatment, diazepam reduced the cSNC effect, indicating that anxiolytics alleviate the contrast effect even under restraint. Together, these results suggest that consummatory suppression is not a byproduct ofenhanced search.