Influence of the noradrenergic state of the nucleus accumbens in basolateral amygdala mediated changes in neophobia of rats.

High responders (HR) and low responders (LR) to novelty coexisting in a normal Wistar rat population were used to examine the effects of combined noradrenergic injections into the basolateral amygdala (BLA) and nucleus accumbens (ACC) on gustatory neophobia in a novel environment. During novelty, HR were marked by a high and LR by a low functional noradrenergic activity in ACC. Water-treated HR and LR mostly consumed familiar rat chow, indicating a high level of neophobia. The effects of BLA injections with noradrenergic agents differed completely between rat types. Propranolol, a beta-adrenergic antagonist, reduced neophobia in HR, but was ineffective in LR, whereas the respective agonist isoproterenol decreased neophobia only in LR. Subsequent ACC injections of noradrenergic agents modulated the effects of the noradrenergic BLA injections on neophobia in line with the theory of amygdala-accumbens gating of information (A. R. Cools, R. Van den Bos, G. Ploeger, & B. A. Ellenbroek, 1991).