Spatial learning/memory and social and nonsocial behaviors in the spontaneously hypertensive, Wistar-Kyoto and Sprague-Dawley rat strains.

The Spontaneously Hypertensive rat (SHR) is often described as less behaviorally reactive than its normotensive strain, the Wistar-Kyoto (WKY), although results are somewhat inconsistent across studies. In part, this may be due to the lack of a definitive characterization of "reactivity." Still, results from identical behavioral tests of SHR and WKY across studies are sometimes conflicting. Further, few comparisons with other rodent strains are available and these might provide guidance in outlining the meaning of reactivity. Here, social and nonsocial behaviors and spatial learning and memory were measured in male and female SHR, WKY, and Sprague-Dawley (SD) rats. Systolic blood pressure measurements at adulthood confirmed hypertension in the SHR. Juvenile play behavior indicated that SHRs were more sensitive to the strain of their play partner than were the WKY or SD, playing less with different strain partners than with same strain partners. However, adult dominance behavior (restricted access in a water competition test) indicated no strain differences. The SHR appeared to exhibit attenuated acoustic startle relative to the WKY and SD and their prepulse inhibition was substantially less at higher prepulse decibel intensities; however, this decreased prepulse inhibition was not the result of decreased startle during the test. Anxiety-related behavior in the elevated plus maze was most prominent in the SD strain, possibly as a result of poorer motor coordination as measured by rotarod performance. Elevated plus maze behavior as well as motor coordination did not differ between the SHR and WKY strains. Performance in the NCTR complex maze and the Morris water maze was significantly better in the SHR. These results do not support hypotheses of decreased behavioral reactivity in the SHR strain. Rather, they suggest complex interactions between social and nonsocial environments and the behavioral capabilities and requirements of the rat strain.