Nadia Justel

Effects of pretraining treatment with testosterone on successive and anticipatory negative contrast

Previous research indicated that the suppression of consummatory behavior that follows incentive downshift in male rats is attenuated by testosterone (T) administration during training. The present experiments were designed to assess the role of pretraining T administration on two incentive contrast situations in consummatory behavior: successive negative contrast (cSNC) and anticipatory negative contrast (cANC). In cSNC (Experiment 1), a downshift from 32% to 4% sucrose leads to behavioral suppression relative to an unshifted, 4% sucrose condition (the cSNC effect). Pretraining T administration enhanced consummatory behavior directed at 4% sucrose, without affecting behavior directed at 32% sucrose. This effect obscured a reduction in the cSNC effect by the T treatment that was only detected when a proportional measure of behavior was used. In cANC (Experiment 2), groups received access to two bottles per day separated by a short midtrial interval. Consumption of 4% sucrose is suppressed when the second bottle offers 32% sucrose, relative to 4% sucrose (the cANC effect). Pretraining T did not affect the cANC effect, known to be insensitive to treatment with anxiolytics. These results suggest an anxiolytic-like effect of testosterone in adjustment to incentive downshifts.

Cholinergic transmission underlies modulation of frustration by open field exposure

Frustration can be defined as an emotional state generated by the omission or devaluation in the quantity or quality of an expected appetitive reward. Thus, reactivity to a reward is affected by prior experience with the different reinforcer values of that reward. This phenomenon is known as incentive relativity, and can be studied by different paradigms. Although methodologically simple, the exploration of a novel open field (OF) is a complex situation that involves several behavioral processes, including stress induction and novelty detection. OF exposure can enhance or block the acquisition of associative and non-associative memories. These experiments evaluated the effect of OF exploration on frustration and the role played by the cholinergic system in this phenomenon. OF exploration before first or second trial of incentive downshift modulated the expression of frustration. This effect of OF was blocked by the administration of scopolamine either before or after OF exploration. These results indicate that the cholinergic system is involved in the acquisition and consolidation of OF information.

Open field exposure facilitates recovery from an aversive emotional event: Involvement of adrenergic and cholinergic transmitter systems

Successive negative contrast (SNC) is an incentive relativity procedure that has been widely used to model emotional reactivity in rodents. The reward downshift experienced during SNC is thought to result in frustration. The exploration of a novel open field (OF), a complex situation involving stress induction and novelty detection, can enhance or block the acquisition of associative and non-associative memories. Previous experiments found a modulatory effect of OF, applied before downshift trials, on SNC. This schedule, however, can affect retention performance by influencing attentional, motivational, motor or sensory-perceptual mechanisms at training or retention testing. The use of post-training OF exposure avoids these confounds. This work assessed the effect of OF exposure after the acquisition of the downshifted memory, with the goal of targeting the consolidation of this mnemonic trace. We also investigated the involvement of the cholinergic and adrenergic systems in this phenomenon. The results indicated that OF facilitates recovery from reward loss and that both transmitter systems, cholinergic and adrenergic, play a role in this effect of OF.