SHRs show increased levels of rearing activity. Naïve SHR and WIS rats were exposed to an activity/open field box for 1 h on day one (see Figure 1) and were re-exposed to the same testing box for two consecutive days. (A) Average number of rears during the initial 10 min of testing. (B) Average number of rears during the 20-60 min interval of testing. All data are represented as mean ± S.M.E. (N = 5 animals per group). *P < 0.05, **P < 0.001 when compared to WIS rats.