Genetic Disruption of System xc- Mediated Glutamate Release from Astrocytes Increases Negative-Outcome Behaviors While Preserving Basic Brain Function in Rat

Abstract

The impact of CNS disorders is exacerbated by the difficulty in developing safe, effective glutamatergic therapeutics. Synaptic glutamate transmission is vital for neural physiology throughout the brain, which contributes to the vast therapeutic potential and safety risk of glutamatergic therapeutics. Here, we created a genetically modified rat (MSxc) to survey the range of brain functions impacted by the loss of glutamate release from astrocytes involving system xc- (Sxc). Eliminating Sxc activity was not lethal and did not alter growth patterns, activity states, novel object recognition or performance of other simple tasks. In contrast, MSxc rats differed from WT in Pavlovian Conditioned Approach and cocaine self-administration/reinstatement paradigms. Both WT and MSxc rats readily learned that a cue predicted food delivery during Pavlovian Conditioned Approach training. However, WT rats were more likely to approach the food tray (i.e., goal tracking) whereas MSxc rats were more likely to approach the food-predicted cue (i.e., sign tracking) even when this behavior was punished. In the self-administration/reinstatement paradigm, MSxc rats had higher levels of cocaine-primed drug seeking in the absence of altered extinction or cocaine self-administration. These data demonstrate that Sxc-mediated glutamate release from astrocytes regulates non-reinforced and negative-outcome behaviors without altering simple learning or other forms of basic brain function.