Age-related peculiarities in steroid hormone secretion and behavior in prenatally stressed female rats in novel environment.

We studied the effects of immobilization of female rat during days 15-18 of pregnancy on the behavior in novel environment (open field test) and blood level of steroid hormones in their female offspring depending on the cycle phase and age. The rats were tested at the age of 3, 12, and 24 months. Locomotor and exploratory activity and anxiety of control rats depended on the phase of estrous cycle. Age-related changes in the studied parameters were noted: locomotor and exploratory activity decreased and anxiety increased against the background of reduced secretion of the main ovarian hormones with age. In addition, blood estradiol level and behavior in novel environment virtually did not depend on age and estrous cycle phase in prenatally stressed females. Our findings suggest that maternal stress has a modulatory effect on relationship between behavioral type and estrous cycle stage, as well as on age-related pattern of behavioral reactions.

[Effects of social isolation during puberty on reproductive functions and behavior of prenatally stressed female rats].

We studied the consequences of keeping in isolation (1 animal per cage) during the puberty period of female rats born from intact mothers or from mothers suffering an 1-hour immobilization stress in the last trimester of pregnancy, and its influence on oestrous cycle and anxiety level of the adult offspring. There were no changes in the rates of anxiety level depending on oestrous cycle phase among both control and prenatally stressed females in isolation. On rats moving to the groups (4-5 animals per cage) the control rats unlike the prenatally stressed individuals show this dependence. About 50 % of the control and experimental rats, grown in isolation, are characterized by reduction ofoestrous cycle duration (3.3 +/- 0.05 days). The rest of the animals have the normal duration ofoestrous cycle (4 +/- 0.3 days), or prolonged duration (5 +/- 0.25 days). The control rat's oestrous cycle increased because ofdioestrus phase, whereas prenatally stressed rats oestrous cycle increased because of estrus phase. On females moving to groups the estrous cycle duration of most rats increased, but among the prenatally stressed rats there were still females with prolonged estrus phase. Besides, the prenatally stressed rats moved from isolation to groups has the reduced blood level of corticosteroid, and the control rats has an increased one. According to our opinion, under the conditions of low population density the prenatal stressed animals show better adaptive reaction because the estrous cycle reduction and the estrus phase prolongation make the possibility of pregnancy higher.

[Changes in the uterus morphometric parameters in prenatally stressed rats].

The effects of immobilization stress from 15th to 18th days of gestation on morphometric parameters of the adult offspring uterus were studied. The results showed that there were no changes of endometrial morphometry in respect to oestrous cycle in 3-month prenatally stressed female. Prenatal stress decreased the myometrium thickness in oestrus and diestrous owing to circular muscle layer. These data suggested that influence of prenatal stress on morphometric parameters of the rat uterus was induced by disturbance of sex steroid secretion.

[The hypothalamic-pituitary-adrenal axis, and reproductive system activity changing of female rats with prenatal stress during aging].

The effect of female rat daily 1-hour immobilization in the period from the 15th to the 18th gestation days on the sex steroid secretion subject to estrous cycle, hypothalamic-pituitary-adrenal axis (HPA) activity and its sensitivity to regulatory signals based on the mechanism of negative feedback in ternale offspring during different ontogenesis stages, was studied. It has been shown that prenatal stress causes significant reproductive system activity disturbances, leading to a significant decrease in the HPA sensitivity to feedback signal in aging female rats. The obtained data indicate a modifying influence of mothers' stress on changing of female rat reproductive functions during aging together with influence on significant decrease in efficiency of HPAs' feedback path.

[Sensitiveness to social stress in female rats with alteration of the pituitary-adrenal axis stress reactivity].

The sensitiveness of female rats to social stress induced by increasing group density, was investigated. It was shown that female rats were housed in groups of 9-10 animala per cage in pubertal period and demonstrated significant alteration of oestrous cycle duration and anxiety level. This housing condition increased basal level of corticostcrone in prenatal stressed female rats who have high stress reactivity of the hypothalamic-pituitary-adrenal axis, as well as a more profound effect on anxiety level and oestrous cycle. Prenatal stressed rats retained impairment of oestrous cycle and behavior after optimization of housing condition, whereas control rats demonstrated normalization of oestrous cycle duration and anxiety level. These data suggest that high stress reactivity females rats are more sensitive to crowding-induced stress.