The QTL analysis was performed in order to identify the genetic loci that contribute to the behavior in the open field tests in the ISIAH rat strain with inherited stress-induced arterial hypertension. Two F2 populations of 3-4-month-old (n = 106) and 6-month-old (n = 130) male rats derived from a cross between the normotensive Wistar albino Glaxo (WAG) and hypertensive ISIAH rats were used in the search for the QTL. In 3-4-month-old rats, QTL were found: a) for the rat locomotion at the periphery of the open field in the region of D2Rat157-D2Rat88 markers (logarithm of odds (LOD) score 4.83; p= 0.000058) on Chr. 2 and in the vicinity of the D16Rat32 marker (LOD score 3.71; p = 0.00023) on Chr. 16. These two QTL describe the 42.9% of the trait variability. b) for the rat locomotion during the first minute of the open field test on Chr.16 near the D16Rat58 marker (LOD score 3.78; p = 0.00028). The results provided support for the existence of the age-dependent differences in the genetic control of the traits analyzed.