Decreased striatal c-Fos accompanies latent inhibition in a conditioned taste aversion paradigm

Abstract

Latent inhibition (LI) is a phenomenon whereby previous exposure to a stimulus retards subsequent acquisition of a conditioned response to that stimulus. The present study investigated the neuronal substrates of LI as assessed in a conditioned taste aversion paradigm by comparing regional c-Fos activation in pre- vs. non-pre-exposed animals. The LI paradigm involved a pre-exposure phase in which water-deprived rats were allowed access to either water (non-pre-exposed; NPE) or 5% sucrose (pre-exposed; PE), followed by a conditioning phase in which animals were allowed access to sucrose and subsequently injected with lithium chloride, and a test phase in which animals were allowed access to both sucrose and water. LI was assessed by comparing the %-sucrose consumed in PE and NPE groups on the test day. Two hours following the onset of the test phase, animals were perfused and their brains processed for c-Fos immunohistochemistry. PE animals drank significantly more sucrose on the test day, indicating the presence of LI. PE animals had significantly fewer FLI-positive cells in the striatum than NPE animals; however, no differences were seen in the nucleus accumbens. This difference in FLI was not due to a difference in sucrose consumption on the test day as there was no correlation between c-Fos and amount of sucrose consumed in the PE group. These data are consistent with previous data supporting a role for the striatum in the disruption of LI as assessed by CTA.