Physostigmine and norepinephrine: Effects of injection into the amygdala on taste associations

The present investigation was conducted to determine whether norepinephrine or acetylcholine systems of the amygdala could be involved in two adaptive feeding behaviors in the rat: development of taste aversion and recovery from neophobia. In a taste aversion paradigm, a single bilateral injection of physostigmine directly into the amygdala at the onset of an apomorphine-induced illness experience produced a time-dependent attenuation in the development of taste aversion; in contrast, norepinephrine had no disruptive effects. In a neophobia paradigm, norepinephrine injected directly into the amygdala after a novel taste experience resulted in a time-dependent attenuation in recovery from neophobia; however, physostigmine produced no disruptive effects. Hence, acetylcholine appears to mediate taste-illness associations, while norepinephrine plays an important role in recovery from neophobia, i.e., taste-“learned safety” associations.