Contrasting lever-press avoidance behaviors of spontaneously hypertensive and normotensive rats (Rattus norvegicus)

Lever-press avoidance performances of Spontaneously Hypertensive (SHR) and Wistar-Kyoto (WKY) rats were observed in two experiments. The first compared them at shock intensities of 1 or 2 mA. The SHRs had the highest percentage of avoidances, made the most coping responses (avoidances plus escapes), and received the fewest shocks (ps less than .05). They also had shorter avoidance and initial-escape latencies (ps less than .05). In the second experiment these strains were trained with signal-shock intervals that produce good (60 s) or poor (10 s) avoidance acquisition. Analysis of the Strain x Conditions x Blocks interaction showed that SHRs performed better with the longer interval (p less than .05), whereas WKYs' performance was similar with both (p greater than .05). Thus WKYs differed from all other strains previously exposed to these conditions. The findings are interpreted in terms that emphasize the SHRs' tendency to move, compared with the WKYs' tendency to freeze in response to aversive stimuli, rather than characterizing SHRs as hyperreactive.