Variation in the Form of Pavlovian Conditioned Approach Behavior among Outbred Male Sprague-Dawley Rats from Different Vendors and Colonies: Sign-Tracking vs. Goal-Tracking

Abstract

Even when trained under exactly the same conditions outbred male Sprague-Dawley (SD) rats vary in the form of the Pavlovian conditioned approach response (CR) they acquire. The form of the CR (i.e. sign-tracking vs. goal-tracking) predicts to what degree individuals attribute incentive salience to cues associated with food or drugs. However, we have noticed variation in the incidence of these two phenotypes in rats obtained from different vendors. In this study, we quantified sign- and goal-tracking behavior in a reasonably large sample of SD rats obtained from two vendors (Harlan or Charles River), as well as from individual colonies operated by both vendors. Our sample of rats acquired from Harlan had, on average, more sign-trackers than goal-trackers, and vice versa for our sample of rats acquired from Charles River. Furthermore, there were significant differences among colonies of the same vendor. Although it is impossible to rule out environmental variables, SD rats at different vendors and barriers may have reduced phenotypic heterogeneity as a result of genetic variables, such as random genetic drift or population bottlenecks. Consistent with this hypothesis, we identified marked population structure among colonies from Harlan. Therefore, despite sharing the same name, investigators should be aware that important genetic and phenotypic differences exist among SD rats from different vendors or even from different colonies of the same vendor. If used judiciously this can be an asset to experimental design, but it can also be a pitfall for those unaware of the issue.

Adolescent Alcohol Exposure Amplifies the Incentive Value of Reward-Predictive Cues Through Potentiation of Phasic Dopamine Signaling

“…We cannot entirely rule out the possibility that housing conditions contribute to the overall pattern of conditioned responses reported here. However, control animals, housed in the identical conditions to that of the alcohol-exposed animals, show a distribution of conditioned responses that is consistent with previous work that systematically examined the population statistics of these behaviors (Fitzpatrick et al, 2013). This would suggest that singly housing animals in the current work did not shift the overall distribution of response biases and is therefore not the likely explanation for the extreme shift in the alcohol group exclusively to sign-tracking behavior.…”

Isolating the incentive salience of reward-associated stimuli: value, choice, and persistence

“…Furthermore, the homogeneity of the sample used here could also be a contributing factor; although we know not in what colony rooms our animals were bred, they were all from Harlan Laboratories (Indianapolis, IN). As stated in the introduction, Fitzpatrick et al (2013) observed variation in the uniformity of sign-tracking behavior to a lever between cohorts of rats acquired from Harlan Laboratories and Charles River Laboratories (Wilmington, MA), where rats from Harlan Laboratories showed a sign-tracking bias that was modulated by breeding colony room. Finally, an additional factor that could be of interest is the type of lever stimulus used.…”

“…Holland et al 2014), an issue that may be partially related to differences in animal vendors or even breeding colonies within vendors (Fitzpatrick et al 2013). Furthermore, because identification of the response cohorts is based on PCA performance, study of the processes involved in the acquisition of sign-and goal-tracking behavior is problematic; although the use of a genetic model has been used for the study of sign-and goal-tracking response acquisition (Flagel et al 2011), selective breeding comes with its own set of problems (e.g., inadvertent neurobehavioral changes not intentionally selected).…”

Genome wide association analysis in a mouse advanced intercross line

“…We have previously shown that GBS is a cost-effective strategy for genotyping CFW mice 282 (Fitzpatrick et al 2013). The advantages of GBS were even greater for this AIL because imputation 283 allowed us to easily obtain 4.3M SNPs while using only half the sequencing depth (Fig.…”