Reward Devaluation Attenuates Cue-Evoked Sucrose Seeking and Is Associated with the Elimination of Excitability Differences between Ensemble and Non-ensemble Neurons in the Nucleus Accumbens

Abstract

Animals must learn relationships between foods and the environmental cues that predict their availability for survival. Such cue-food associations are encoded in sparse sets of neurons or "neuronal ensembles" in the nucleus accumbens (NAc). For these ensemble-encoded, cue-controlled appetitive responses to remain adaptive, they must allow for their dynamic updating depending on acute changes in internal states such as physiological hunger or the perceived desirability of food. However, how these neuronal ensembles are recruited and physiologically modified following the update of such learned associations is unclear. To investigate this, we examined the effects of devaluation on ensemble plasticity at the levels of recruitment, intrinsic excitability, and synaptic physiology in sucrose-conditioned Fos-GFP mice that express green fluorescent protein (GFP) in recently activated neurons. Neuronal ensemble activation patterns and their physiology were examined using immunohistochemistry and slice electrophysiology, respectively. Reward-specific devaluation following 4 d of ad libitum sucrose consumption, but not general caloric devaluation, attenuated cue-evoked sucrose seeking. This suggests that changes in the hedonic and/or incentive value of sucrose, and not caloric need, drove this behavior. Moreover, devaluation attenuated the size of the neuronal ensemble recruited by the cue in the NAc shell. Finally, it eliminated the relative enhanced excitability of ensemble (GFP ϩ) neurons against non-ensemble (GFP Ϫ) neurons New Research

Acute, but not longer‐term, exposure to environmental enrichment attenuates Pavlovian cue‐evoked conditioned approach and Fos expression in the prefrontal cortex in mice

“…On test day, our mice did not directly experience sucrose reward. However, we and others have shown that conditioned approach responses evoked by Pavlovian sucrose cues are under the control of retrieving a representation of the sucrose reward, as it is sensitive to devaluation manipulations ( Sieburg et al, 2019 ). From this perspective, our mice may have attributed greater reward value to the recent EE experience compared with the retrieved representation of sucrose, thus resulting in a negative contrast effect ( Grimm & Sauter, 2020 ).…”

“…Following acquisition of this simple CS-US association, sucrose-seeking behavior is assessed by measuring approach and responding (i.e. head entry) to the sucrose delivery site during the (non-reinforced) sucrose-associated CS ( Blaiss & Janak, 2009 ; Day et al, 2006 ; Sieburg et al, 2019 ; Ziminski, Hessler, et al, 2017 ). Next, because Fos expression increases in different corticoaccumbens areas in response to non-contingent food CS exposure ( Brebner et al, 2020 ; Haight et al, 2017 ; Schroeder et al, 2001 ; Ziminski, Hessler, et al, 2017 ), we compared “Fos” expression across different EE conditions in the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), and nucleus accumbens (NAc).…”

Astrocytes in the external globus pallidus coordinate flexibility of action strategy

“…Goal-directed behaviors and habits can be quickly and e ciently developed by the random ratio (RR) task with effort-based reward delivery and the random interval (RI) task with time-based reward delivery 4 . We used sucrose solution as a reward since it has an intense rewarding effect in mice, especially in operant conditioning [13][14][15] . Upon nose-poke in an active hole, 10 µl of 20% sucrose solution was immediately delivered in the magazine through an automated syringe as we previously described [16][17][18] .…”

“…As previously described 17,18 , we utilized sucrose as a reward. After fasting, mice are highly motivated to seek out sucrose, which facilitates the operant learning 14 . Although sucrose is not fully representing the addictive drugs 50 , sucrose has common rewarding and reinforcing properties as substance abuse, especially in rodents 15,51 .…”

Optogenetic interrogation of the role of striatal patches in habit formation and inhibition of striatal dopamine

“…In addition to lever pressing, head entry to the food magazine has been used to assess flexibility (DePoy et al, 2016; Morrison et al, 2015; Sieburg et al, 2019). ChR2 mice and YFP controls both altered their entry rates across training (two-way repeated measures ANOVA, significant effect of time, F (14, 392) = 5.148, p <0.0001), though ChR2 mice tended to have higher entry rates (trending effect of group, F (1, 28) = 3.204, p = 0.0843; no significant interaction, p > 0.05; Figure 2F).…”