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Biomedical subjects

D A Zhukov

Publications and source records attributed to D A Zhukov.

At least 19 recordsLinked to original sources
PubMed2003

The effects of stages of the estrous cycle on pain thresholds in female white rats.

The effects of stages in the estrous cycle on electrical pain thresholds were studied in white rats in conditions of chronic measurement. On recording day 3, females in the diestrus and estrus stages showed sharp increases in shudder and paw-shuffling thresholds. Females in proestrus and metestrus showed no change in thresholds as compared with those in the first days of recording. Starting from day 7, there were progressive decreases in electrical pain thresholds regardless of the stage of the estrous cycle. Data for all animals showed that regular measurement of pain thresholds induces a smooth two-fold increase in body resistance from day 1 to day 7. This was followed by a sharp drop on day 8, with parallel decreases in body resistance and electrical pain thresholds. Thus, chronic measurement of electrical pain thresholds and body resistance changed in a complex fashion, and threshold values depended on the stage of the estrous cycle.

Animals↗
PubMed2001

[Feedback in the stimulus-response system determines stress specifics].

The paper surveys controllability in the stress theory. Uncontrollable action is perceived by living organisms in a principally different way than the controllable one and induces persisting pathological changes. The controllability, i.e. presence of a feedback in the stimulus/response system, is determined by an interaction of the medium factors and a strategy of subject's behaviour. A passive strategy proves to be optimal for adaptation under the conditions when an animal cannot change unfavourable medium conditions. The authors base their theoretical statements on their own experimental studies as well as literature references analysis.

Adaptation, Physiological↗
PubMed2001

[Effect of estrous cycle phase on pain threshold in female white rats].

Pain thresholds and body resistance in female Wistar rats were determined during estrous cycle stages. The flinch and shuffle thresholds were increased on the 3rd day of measurement in diestrus and estrus but not in proestrus and metestrus as compared with the thresholds during the 1st day of recording. The thresholds decreased as of the 7th day to the 14th day. Daily threshold measurements raised the body resistance on the 7th day of recording. In contrast to the pain thresholds, the body resistance change had not a stage-dependent character.

Animals↗
PubMed1996

[The effect of controllable and uncontrollable stressor actions on dexamethasone receptor binding in the hypophysis and hippocampus of rats with different behavioral strategies].

Exposure to inescapable foot shocks (ISs) decreased the dexamethasone receptor binding in the KHA rat hippocampus. Both the ISs and escapable foot shocks (ESs) enhanced the binding in the pituitary of the KLA rats as well as their plasma corticosterone. The data obtained suggest that the brain corticosteroid binding depends on the coping style of the subject as well as on the stress controllability factor.

Animals↗
PubMed1996

[Agonistic behavior during stress inhibits the development of learned helplessness in rats].

Male Wistar rats were exposed to inescapable shock in individual chambers (IS), or shocked in pairs (PIS). The latter rats were fighting during the shock administration. In 48 hrs, all the rats were subjected to escape/avoidance task in a shuttle-box. Failures increased significantly in the IS rats as compared with the PIS and intact rats. Dexamethasone administration decreased the plasma corticosterone level in the latter groups, but not in the IS rats. The findings suggest that an inescapable shock induces no learned helplessness in rats having an opportunity of agonistic interaction during the shock. The findings suggest also a stress-protective effect of agonistic contacts under averse conditions.

Agonistic Behavior↗
PubMed1994

Inescapable shock induces the opposite changes of the plus-maze test behavior in rats with divergent coping strategy.

Behavior in the elevated plus-maze and plasma corticosterone levels were investigated in Koltushi high-avoidance (KHA) and low-avoidance (KLA) rat strains subjected to inescapable shock (IS) or daily handling for 10 days. These strains have been genetically selected on the basis of divergent acquisition of a conditioned avoidance response in a two-way shuttle-box. Naive KHA rats were more anxious than KLA ones. Following exposure to IS, the time spent in open arms was increased in KHA rats but decreased in KLA rats. After handling, the time spent in open arms increased only in KHA rats and became similar in both strains. There were no differences in plasma corticosterone levels between naive animals. Exposure to either IS or handling increased the plasma corticosterone levels in KLA rats. In KHA rats, handling reduced the plasma corticosterone levels, and exposure to IS had no effect. The present results suggest that the stress-induced changes in anxiety levels depend on the coping strategy of the subject.

Adaptation, Psychological↗
PubMed1994

[The oxytocinergic neurosecretory system in genetically selected rats differing by their emotionality. Morphometric research].

The rats selectively bred for rapid (KHA) and slow (KLA) acquisition of the avoidance response were subjected to inescapable shock (IS). Synthesis and secretion of oxytocin (OT) were higher in intact KLA rats as compared to KHA ones. Preliminary exposure to IS resulted in opposite changes of the OT synthesis and secretion. The findings suggest a dependence of the stress-reactivity of the OT-ergic system on the copying of the behaviour strategy.

Animals↗
PubMed1993

Strain-dependent escape deficit in two rat models of learned helplessness.

The shuttle box escape deficit produced by prior inescapable shock (IS) or by escapable shock (ES) was investigated in Koltushi high- (KHA) and low-avoidance (KLA) rat strains, genetically selected on the basis of divergent acquisition of a conditioned avoidance response in a two-way shuttle box. IS enhanced escape failures only in KHA rats. In contrast, ES produce escape deficit only in KLA rats. These data suggest that the learned helplessness interpretation of escape deficit might be relevant only when IS is administered to KHA rats. In the case of KLA rats exposed to ES, escape deficit represents a coping behavior.

Animals↗
PubMed1993

The dexamethasone suppression test in genetically different rats exposed to inescapable and escapable electric shocks.

The Dexamethasone Suppression Test (DST) was applied to male rats of Koltushi high- (KHA) and low-avoidance (KLA) strains, genetically selected on the basis of divergent acquisition of a conditioned avoidance response in a two-way shuttlebox. Rats were exposed to either inescapable (IS) or escapable (ES) electroshock. IS produced escape deficit in a shuttle box only in KHA rats. ES enhanced escape failures only in KLA rats. There were no differences in plasma corticosterone levels between naive KLA and KHA rats. IS led to increase of the post-dexamethasone corticosterone levels in KHA rats, while both basal and stress-induced corticosterone levels in the KHA strain remained unchanged following IS. In KLA rats exposed to IS, both pre- and post-dexamethasone basal corticosterone levels were increased and stress-induced corticosterone levels were decreased. Thus, resistance to the DST after IS occurred only in KHA rats. ES led to enhanced basal and reduced stress-induced corticosterone levels in KLA rats compared to KHA rats before and after dexamethasone treatment. These findings suggest that the HPA axis reactivity following aversive stimuli depends on the interaction between genotype and stressor controllability.

Animals↗
PubMed1993

[An increased vasopressin level in the blood plasma--a possible cause of dexamethasone resistance in rats following stress].

The dexamethasone sensitivity of the hypothalamo-pituitary-adrenal (HPA) axis was significantly impaired in Wistar rats exposed to inescapable shock. No difference was found between the rats with learned helplessness and intact animals. The feedback impairment seems to occur irrespectively of the hyperactivity of the HPA axis. Inescapable shock increases the plasma vasopressin level which, in its turn, may cause the dexamethasone resistance of the HPA axis.

Animals↗
PubMed1991

[A comparison of the reactions of the hypophyseal-adrenal system in rats to inhibitory and excitatory stimuli].

The basic and stress-induced levels of corticosterone were studied prior to and after administration of dexamethasone (5 micrograms/kg) in 36 male Wistar rats. No correlations between the responses to stress and dexamethasone administration were revealed. The mechanisms regulating excitation and inhibition of the hypophyseal-adrenal system seem to be independent of each other. The values of the corticosterone concentration in the blood plasma during and after dexamethasone administration were shown to be distributed according to the log-normal law.

Animals↗
PubMed1990

[Reaction of the hypophysis-adrenal system to dexamethasone as a re flection of adaptive behavior in rats].

In male Wistar rats (180-230 g), adaptive behaviour (the avoidance response, horizontal and vertical activity in open field tests) was compared with the reaction of hypothalamo-pituitary adrenal axis (HPAA) as measured by the corticosterone level in the blood plasma in resting, stress and under the feedback suppression of the HPAA (administration of dexamethasone). The rats with disturbance of adaptive behaviour due to inescapable shock were found to have HPAA feedback inhibition. The basal and stress-induced levels of corticosterone did not differ from the control values in these animals. The adaptive component of behaviour seems to be reflected in the HPAA sensitivity to feedback signals and not to depend on the obviousness of the stress response.

Adaptation, Physiological↗
PubMed1983

[Receptor binding of corticosterone in brain structures participating in regulation of the hypothalamo-hypophyseo-adrenal system].

Binding of corticosterone by the cytosol receptors after hydrocortisone administration was studied in different tissues of rats. A decrease in the specific binding of corticosterone occurred within 24 hrs in all the structures under study. In 3 days the decrease only persisted in the hypophysis and hypothalamus. The data suggest a connection between the long lasting decrease in the cytosol reception of corticosterone in the hypothalamus and hypophysis and the blockade of the hypothalamo-hypophyseal-adrenal system.

18-Hydroxycorticosterone↗