Abstract

Investigating the effect of corticosterone on the acquisition of sign-tracking behavior in female rats from different vendors

Turfe AE, Westbrook SR, Lopez SA, Sanchez Franco V, Bhatti J, Flagel SB
51st Annual Meeting of the Society for Neuroscience. 2022.

Cues in the environment become predictors of biologically relevant stimuli through associative learning. These cues can also become imbued with incentive value, leading to maladaptive behaviors characteristic of numerous psychopathologies. We can model incentive learning in animals using Pavlovian conditioned approach (PavCA) training, where a discrete lever cue (conditioned stimulus, CS) is followed by the delivery of a food reward (unconditioned stimulus, US). Rats that undergo this training will develop a conditioned response directed towards the lever-CS (i.e., sign-trackers), the food cup (i.e., goal-trackers), or vacillate between the two (i.e., intermediate responders). We have previously reported that after a single PavCA session, plasma corticosterone (CORT) levels are higher in male rats that become sign-trackers relative to those that become goal-trackers. We have also found that CORT administration increases the propensity to sign-track in male rats, but appears to do so selectively in rats from Charles River, and not those from Taconic. Here, we assessed the effect of CORT administration on the propensity to sign-track in female rats, and included vendor as a variable of analysis. Adult female rats from either Charles River or Taconic underwent 5 sessions of PavCA training with 3 mg/kg CORT or vehicle injections (i.p.) administered 30 minutes prior to each session. The effect of CORT administration on sign-tracking and goal-tracking behaviors were assessed using several outcome measures, including the number of lever-CS vs. food cup contacts, the probability to approach the lever-CS vs. food cup, and the latency to approach the lever-CS vs. the food cup. In contrast to our prior findings with male rats, CORT administration did not significantly affect sign-tracking behavior in female rats from either vendor. It is important to note, however, that female rats from Charles River displayed significantly greater sign-tracking behavior compared to those from Taconic. These findings support the notion that individual variation and the distribution of behavioral phenotypes differs between vendors. Blood samples were collected and will be analyzed to determine whether differences in baseline CORT levels between rats from different vendors underlie the reported behavioral effects. The effect of estrous cycle is also being examined. These results underscore the importance of reporting vendor in scientific communications and including it as a critical variable of analysis.