COMPARISON OF ANXIETY MEASURED IN THE ELEVATED PLUS-MAZE, OPEN-FIELD AND SOCIAL-INTERACTION TESTS BETWEEN SPONTANEOUSLY HYPERTENSIVE RATS AND WISTAR EPM-1 RATS

On the basis of open-field and plus-maze results it has been proposed that spontaneously hypertensive (SHR) rats are less emotionally reacti ve than their normotensive controls, Wistar-Kyoto (WKY). However, the proposed ''anxiolytic characteristics'' of SHR rats may be questioned in view of the significant hypoactivity presented by WKY rats. In the present study, the behavioral response of spontaneously hypertensive ( SHR) and equally active normotensive Wistar EPM-1 (EPM-1) rats (4-mont h old males, 10-13 animals per group) were evaluated in the open-field , social interaction and elevated plus-maze tests. In the open-field s tudy, no differences were observed for total locomotion frequency and immobility duration, but SHR rats presented a higher central square lo comotion frequency (23.8 +/- 2.1 vs 10.3 +/- 1.6) as compared to EPM-1 . SHR rats also exhibited a greater duration of social interaction whe n compared to EPM-1 rats (mean +/- SEM values were 113.9 +/- 8.7 s for SHR vs 72.7 +/- 8.6 s for EPM-1 rats after 8-min observation). In the elevated plus-maze test, SHR rats presented an increased percent of e ntries (52.8 +/- 3.3 vs 28.3 +/- 4.5) and time in the open arms (65.6 +/- 6.0 vs 11.1 +/- 1.9) as compared to EPM-1 rats, although the total number of arm entries (9.2 +/- 0.9 vs 9.7 +/- 1.0) was unchanged. The se results suggest that the ''anxiolytic behavior'' of SHR rats in rel ation to normotensive controls is not related to differences in motili ty levels.