Rat Strain Differences in Response to an Unexpected Reduction in Reward
Open Access
- Author:
- White, Amanda Marie
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Victoria Anne Braithwaite Read, Thesis Supervisor
Dr. James Harold Marden, Thesis Honors Advisor - Keywords:
- successive negative contrast
laboratory strain difference
individual behavior variation
neuroscience
animal behavior - Abstract:
- Researchers have become increasingly interested in individual variation in genetic expression, a requirement for evolution (Koolhaas et al., 2010). While experimental rodent strains have traditionally been bred for genetic similarity, behavioral variation between these strains does exist (Koolhaas et al., 2010). This thesis project investigated rat strain differences in frustration. Rats of two strains commonly employed for behavioral tasks, Long-Evans and Sprague-Dawley, were evaluated with a common behavioral task in use for several decades, a successive negative contrast (SNC) paradigm (Flaherty, Troncoso, & Deschu, 1979). In SNC, response to a high value reward is contrasted with response to a lower value reward (Flaherty, 1996). The reward value is decreased unexpectedly over a period referred to as the “downshift,” and is thought to induce frustration through violation of the expectation of a high value reward (Flaherty, Troncoso, & Deschu, 1979). To further explore how a frustration response can be exacerbated by environmental conditions, the effect of loss of environmental enrichment, known to induce a negative affective state on the frustration response was also assessed by strain (Burman et al., 2008). Long-Evans rats differed from Sprague-Dawley rats in preshift (p = 0.026) and postshift lick behavior (p = 0.037) and showed more frustration than Sprague-Dawley rats in response to the downshift in reward (p = 0.012). Environmental enrichment had no effects on preshift, postshift, or downshift licks. This study suggests that strain choice should be taken into consideration when interpreting results from behavioral tests and when selecting strains for an experiment, as preexisting differences in strain may prove more powerful than environmental manipulation.