[Sex differences in the cholinergic status of white rats]. / Polovye razlichiia kholinergicheskogo statusa u belykh krys.

Female rats injected with organophosphate inhibitor of acetylcholinesterase chlorophose at doses of 10 mg/kg and 360 mg/kg showed less considerable decrease in blood acetylcholinesterase activity than did male animals. Females compared with males also demonstrated less expressed clinical symptoms of poisoning (salivation, convulsion) after injection of chlorophose at dose of 360 mg/kg. The value of LD50 in female rats was 860 mg/kg, whereas the comparable value in male animals was 700 mg/kg. Following the injection of atropine at doses of 0.1, 0.3, 0.6 mg/100 g female rats showed 2-3 fold increases in basal adrenal and plasma corticosterone levels, but significant decreases in stress-induced corticosterone levels. As for males, the basal and stress-induced values of corticosterone were not significantly affected by atropine administration. These results suggest that functional reserves of cholinergic system and responsiveness of the hypothalamic-pituitary-adrenal axis to cholinergic influence are greater in females than in males. It is concluded that cholinergic status is significantly higher in female rats than in male ones.

[Sex differences in the dynamic response reactions to emotional stress exposures in white rats]. / Polovye razlichiia dinamiki otvetnykh reaktsii na émotsional'nye stressornye vozdeistviia u belykh krys.

The changes of adrenal and plasma corticosterone and adrenal catecholamines were studied in male and female rats during and after short-term (10 min) emotional stress (the sight and squeals of immobilised partners) and emotional-pain stress (immobilisation). Obvious sexual differences in the stress reactions were revealed: females developed the greatest increase in corticosterone levels which returned to initial values within 40-60 min after cessation of the stress. Concentrations of adrenaline decreased in the first 5 min of stress and became normal by the 10th min. Males developed the greatest increase in the corticosterone levels not during stress but 20-40 min after termination of the stressful stimulus. The adrenaline level increased by the 10th min of stress and became normal within 20 min of poststress period. The advantage of "female's" strategy in stress reactions is discussed.

[Sex differences in the age-related dynamics of the reactivity to physiological stressors in white rats]. / Polovye razlichiia vozrastnoi dinamiki reaktivnosti k fiziologicheskim stressoram u belykh krys.

After removal of habitual partners, white female rats revealed a considerable increase in the corticosterone synthesis and secretion. An increase in the hormone secretion but not in its synthesis occurred in young male rats. In ageing male rats, emotional stress induced an increase in the corticosterone synthesis but the hormone did not enter their blood. High responsiveness of the adaptation systems was revealed in female rats through modification of their basal and stress-induced levels of corticosterone during a 72-hour exposure to light and darkness.

[Analysis of factors determining sex differences in stress reactions of white rats]. / K analizu faktorov, determiniruiushchikh polovye razlichiia v stressovykh reaktsiiakh u belykh krys.

Female rats demonstrate more considerable increasing of corticosterone synthesis and secretion in comparison with male ones under the conditions of emotional and emotion-pain stress. These differences are not disappeared after castration. The sexual differences in stress reactions of infants are accompanied by lower sensitivity of their adaptation system in relation to stressors. The adult neonatal androgenized females show the same reactivity as normal females under the condition of emotion-pain stress. It is concluded that the sexual differences in stress reactions are genetically determined.

[Sexual dimorphism in reactions to stress during regular and altered photoperiods]. / Polovoi dimorfizm v stressornoi reaktsii pri obychnom i izmenennom fotoperiode.

Sexual dimorphism of rats in response to physiological stress influences was discovered. The emotional stress in female animals caused a sharp intensification of synthesis and corticosterone secretion, while in males there was an increase only in hormone synthesis and not its secretion. Females are more sensitive even to short-term changes in photoperiod. Stress reaction in females under conditions of three-day light depressed sharply and increased under conditions of three-day darkness. Stress reaction in males did not change under these conditions. The reactivity of adaptation system in females shortens the period of adaptation to the altered illumination regimen, which is manifested in the restoration of typical stress reactions. In males, refractoriness to weak stress influences lengthens the period of adaptation, which is manifested in the suppression of typical stress reaction observed in males.