Nucleus accumbens GABA ergic inhibition generates intense eating and fear that resists environmental retuning and needs no local dopamine

Abstract

Intense fearful behavior and/or intense appetitive eating behavior can be generated by localized amino acid inhibitions along a rostrocaudal anatomical gradient within medial shell of nucleus accumbens of the rat. This can be produced by microinjections in medial shell of either the γ‐aminobutyric acid ( GABA ) A agonist muscimol (mimicking intrinsic GABA ergic inputs) or the AMPA (α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid) antagonist DNQX (6,7‐dinitroquinoxaline‐2,3‐dione), disrupting corticolimbic glutamate inputs). At rostral sites in medial shell, each drug robustly stimulates appetitive eating and food intake, whereas at more caudal sites the same drugs instead produce increasingly fearful behaviors such as escape, distress vocalizations and defensive treading (an antipredator behavior rodents emit to snakes and scorpions). Previously we showed that intense motivated behaviors generated by glutamate blockade require local endogenous dopamine and can be modulated in valence by environmental ambience. Here we investigated whether GABA ergic generation of intense appetitive and fearful motivations similarly depends on local dopamine signals, and whether the valence of motivations generated by GABA ergic inhibition can also be retuned by changes in environmental ambience. We report that the answer to both questions is ‘no’. Eating and fear generated by GABA ergic inhibition of accumbens shell does not need endogenous dopamine. Also, the appetitive/fearful valence generated by GABA ergic muscimol microinjections resists environmental retuning and is determined almost purely by rostrocaudal anatomical placement. These results suggest that nucleus accumbens GABA ergic release of fear and eating are relatively independent of modulatory dopamine signals, and more anatomically pre‐determined in valence balance than release of the same intense behaviors by glutamate disruptions. We investigated whether eating or fear generated by GABA inhibition of accumbens shell depend on local dopamine, and whether the valence of these behaviors can be retuned by changes in environmental ambience, similarly to glutamate blockade. We report that the answer to both questions is ‘no’. These results suggest that GABA‐induced motivated behaviors are both independent of modulatory dopamine signals and more anatomically pre‐determined than the same behaviors elicited by glutamate blockade.