Figure 2.

NAc rostrocaudal differences in glutamate and GABA mediation of desire and dread. Top: Sagittal view showing maps of DNQX- or muscimol-generated appetitive eating vs. fearful or defensive behaviors, and effects of adding local dopamine blockade to the same microinjection. Appetitive eating and defensive reactions elicited by DNQX (top left) both require D1 receptor function (top middle), but defensive reactions additionally require D2 receptor function (top right) (figure is adapted from Richard and Berridge, 2011). By contrast, GABAergic muscimol-generated eating and defensive behaviors (bottom left) are unaffected by dopamine blockade (bottom right) (adapted from Richard et al., 2013). Bottom: Environmental ambience retunes the motivation function of NAc sites. Testing in home environments abolished almost all defensive reactions, and promoted appetitive eating, elicited by DNQX microinjections in NAc shell (top left). By contrast, a stressfully loud and bright environment expanded DNQX-generated defensive behaviors into rostral regions of NAc shell, and suppressed fearful reactions (top right), relative to standard laboratory conditions (top middle). Muscimol microinjections in NAc shell generated eating and fear at similar sites to DNQX, but was not shifted by environmental ambience of home (bottom left), standard (bottom middle), or stressful test conditions (bottom right). Sites are colored as producing appetitive behavior (green sites), defensive behavior (red sites), or mixtures of both behaviors (yellow). Green symbols represent at least a 200% increase in food intake, red symbols represent at least a 500% increase in defensive treading or another defensive reaction (distress vocalization, escape attempt or biting when rat was touched), and yellow symbols represent a combination of the eating and defensive criteria (adapted from Richard et al., 2013).