Effect of previous taste experiences on taste neophobia in young-adult and aged rats.

Neophobia is an innate response that can be defined as the reluctance to consume novel-tasting substances. The differential effect of previous aversive and nonaversive taste memory on a subsequent neophobic response was studied in young-adult (Experiment 1) and aged rats (Experiment 2). Surprising, a previous nonaversive taste experience eliminated the subsequent neophobic response to a solution of 1% sodium chloride (NaCl) in young-adult and aged rats. This result is interpreted as a generalization of the previous safe taste memory and the emotional responses that might be induced when a new taste is presented. However, a differential effect associated with aging was found for a previous aversive taste memory induced with a low dose of lithium chloride (0.15 M; 1% b.w.). While in young-adult rats this aversive taste memory did not change the neophobic response to an NaCl solution, in aged rats this memory potentiated the subsequent neophobic response to NaCl. This result is interpreted as an increase in the generalization of aversive taste memory and the emotional responses associated with aging.