Effect of dehydroepiandrosterone on avoidance behavior of adult male rats

We studied the effect of repeated intraperitoneal treatment with dehydroepiandrosterone in doses of 0.1 and 0.7 mg/kg on conditioned-response activity and behavior of adult male rats. The effect of dehydroepiandrosterone on learning was estimated in conditioned active and passive avoidance response paradigms. Chronic administration of dehydroepiandrosterone in low and high doses had no effect on retention of conditioned passive avoidance response in adult male rats 24 h after learning. However, chronic administration of dehydroepiandrosterone in low dose impaired acquisition of the conditioned active avoidance response. It should be emphasized that chronic administration of dehydroepiandrosterone in high dose did not modulate acquisition and retention of this reaction. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 7, pp. 63–67, July, 2004 This work was supported by the Regional Social Foundation for Russian Medicine.     

Prolonged decrease in stress reactivity caused by dehydroepiandrosterone sulfate

In male rats exposed to repeated stress, the decrease in stress reactivity produced by subcutaneous injection of dehydroepiandrosterone sulfate (recorded by the decrease in stress-induced concentrations of corticosterone and adrenocorticotropic hormone in blood plasma) was observed 1–6 days postinjection and involved central regulatory mechanisms. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 141, No. 5, pp. 507–510, May, 2006     

Ratio between the Contents of 11-Dehydrocorticosterone and Corticosterone after Acute and Repeated Stress: Effect of Dehydroepiandrosterone Sulfate

Acute stress was accompanied by reduction of 11-dehydrocorticosterone to corticosterone in male rats. The reverse reaction predominated during repeated stress and increased after administration of dehydroepiandrosterone sulfate. Treatment with mu-opioid receptor antagonist naltrexone in a dose of 0.1 mg/kg 20 min before administration of dehydroepiandrosterone sulfate abolished this effect.     

Effects of Dehydroepiandrosterone Sulfate on the Conversion of Corticosterone into 11-Dehydrocorticosterone in Stress: A Regulatory Scheme

In male rats, repeated but not single exposures to stress increased the conversion of corticosterone (CS) to 11-dehydrocorticosterone (11-DHCS), particularly on the background of administration of dehydroepiandrosterone sulfate (DHEAS). Naltrexone given 20 min before DHEAS at a dose of 0.1 mg/kg, at which it selectively blocks μ opioid receptors, prevented this effect of DHEAS, which is evidence that it is mediated by μ opioid receptors. This action of DHEAS involved endogenous ACTH and was thus mediated by central regulatory mechanisms. Our results, along with published data, lead to the first proposed scheme for the physiological regulation of the interconversion of CS and 11-DHCS in conditions of repeated stress with the involvement of DHEAS and μ opioid receptors. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 8, pp. 945–951, August, 2008.     

Neurosteroid regulation of inhibitory synaptic transmission in the rat hippocampus in vitro

The effect of the neurosteroid dehydroepiandrosterone sulfate on inhibitory synaptic transmission was studied in area CA1 of the rat hippocampus using an in vitro hippocampal slice preparation. Synaptic responses elicited by stimulation of Schaffer collateral fibers were recorded extracellularly as population spikes in the somatic region and as synaptic field potentials in the dendritic region. Bath application of dehydroepiandrosterone sulfate (10 μM) enhanced the synaptically evoked somatic population spike with no effect on the dendritic synaptic potential. Isolation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor-mediated component of the synaptic response by addition of antagonists of N-methyl- -aspartate and GABA receptors to the perfusion saline demonstrated that dehydroepiandrosterone sulfate had no effect on this component of the dendritic synaptic potential. In contrast, dehydroepiandrosterone sulfate antagonized GABA receptor-mediated inhibitory effects in the somatic region, resulting in an augmentation of the somatic population spike amplitude. Paired-pulse facilitation was unaltered by dehydroepiandrosterone sulfate, thus arguing against possible presynaptic sites of dehydroepiandrosterone sulfate's actions.These results indicate that dehydroepiandrosterone sulfate can alter synaptic transmission in the hippocampus through selective postsynaptic actions on inhibitory synaptic transmission. A synaptic effect of dehydroepiandrosterone sulfate is consistent with a neuromodulatory role for this neurosteroid in the central nervous system, and may contribute to the reported effects of dehydroepiandrosterone sulfate on cognitive processes such as learning and memory.     

Interleukin-2 concentration in hypothalamic structures of rats receiving peptides during mild stress

The number of hypothalamic IL-2-containing cells changed in rats receiving Vilon and Epithalon during mild stress (handling). The number of IL-2-positive cells in hypothalamic structures decreased 24 h after intramuscular injection of Epithalon and 2 h after intranasal administration of the test peptides. Adaptation of animals to experimental conditions prevented the decrease in the number of IL-2-positive cells in the supraoptic nucleus after intranasal administration of Epithalon. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 4, pp. 371–374, April, 2006     

Ultrastructure of neurons in the hypothalamic suprachiasmatic nucleus of rats with different stress reactivity

The rats were divided into groups demonstrating extremely high and low stress reactivity depending on the results of testing for the nociceptive threshold and thermolability in response to bacterial lipopolysaccharide administration. Specific structural features of the nucleus and mitochondria were revealed in neurons of the hypothalamic suprachiasmatic nucleus in rats with constitutionally high reactivity, which reflects high functional activity and stress-induced lability of these structures. Ultramicroscopic study revealed phenotypic differences in one of the key hypothalamic nucleus, which enables potent and rapid neurogenic response of the stress system in animals with high stress reactivity. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 11, pp. 578–581, November, 2007     

Hypothalamic-pituitary-adrenal system and enzymes of the glutathione-dependent antioxidant system during stress and aging

Activity of glutathione-dependent antioxidant enzymes (glutathione peroxidase, glutathione reductase, and glutathione transferase) in blood erythrocytes from female Macaca mulatta (6–8 and 20–26 years) was measured during activation of the hypothalamic-pituitary-adrenal system under conditions of acute psychoemotional stress (2-h restraint stress). Glutathione reductase activity increased during stress, depended on the time of day, and strongly correlated with blood corticosteroid level. Circadian variations in stress reactivity of glutathione reductase during aging were accompanied by similar changes in stress reactivity of the hypothalamic-pituitary-adrenal system. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 11, pp. 574–577, November, 2007     

Protective and therapeutic effects of glyprolines in psychoemotional stress induced by cholecystokinin-4 injection

Experiments on outbred albino male rats showed that psychoemotional stress induced by intraperitoneal injection of cholecystokinin-4 (100 μg/kg) increased anxiety, impaired orientation and exploration activities in the elevated plus-maze and hole-board tests, and increased the level of depression of Porsolt test. Preliminary intranasal administration of glyprolines (15 min before cholecystokinin) in a dose of 3.7 μmol/kg prevented the development of stress-induced behavioral disturbances. Administration of peptides 30 min after cholecystokinin-4, i.e. to rats with developed behavioral disturbances, almost completely abolished these disturbances. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 3, pp. 270–274, March, 2008     

Role of the hypothalamic suprachiasmatic nucleus in the effect of melatonin on the thymus, adrenal glands, and spleen in rats

We studied the role of the hypothalamic suprachiasmatic nucleus in realization of the effect of melatonin on stress marker organs in rats under normal conditions and during acute stress. Stress induced involution of the thymus in active rats and adrenal gland hypertrophy in active and passive animals. Electrocoagulation of the suprachiasmatic nucleus induced a more pronounced decrease in the weight of the thymus and greater increase in the weight of the adrenal glands. Melatonin administration after electrocoagulation of the suprachiasmatic nucleus had no effect on the relative weight of the thymus, adrenal glands, and spleen in control and stressed animals. The influence of melatonin on the thymus, adrenal glands, and spleen is partly mediated by this structure of the brain. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 4, pp. 364–367, April, 2006     

Effect of prolonged emotional and pain stress on the content of methylcytosine-binding protein MeCP2 in nuclei of hippocampal neurons in rats with different excitability of the nervous system

In rats with low excitability threshold of the nervous system demonstrating significant and persistent behavioral disorders under stress conditions, the content of methylcytosine-binding protein MeCP2 in neuronal nuclei of hippocampal field CA3 decreased over 2 weeks after long-term emotional and pain stress. It was hypothesized that protein MeCP2 triggers epigenetic changes in DNA that underlie “stress memory”. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 8, pp. 205–207, August, 2006     

Distribution of thietazole in organs and tissues of rats after single and repeated administration

We studied the kinetics of thietazole distribution in the liver, brain, kidneys, spleen, heart, skeletal muscles, lungs, adipose tissue, and testicles after single and repeated administration of this drug. Single and repeated administration of thietazole was followed by elimination of this drug from the blood into organs and tissues. After repeated administration, thietazole was selectively accumulated in the spleen. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 5, pp. 555–557, May, 2008     

Short-term cold exposure improves antioxidant status and general resistance of animals

We studied the effect of short-term swimming in cold water (13°C) on parameters of the blood antioxidant system (activities of superoxide dismutase and catalase, concentrations of ceruloplasmin and nonprotein thiols), heme oxygenase activity, and nonprotein thiol level in mouse liver. The test parameters of antioxidant protection increased 1 h after cold exposure and remained high 1 day after treatment. These changes were accompanied by an increase in the adaptive capacity. After swimming in cold water the resistance of animals to another stress factor (administration of epinephrine) was higher compared to controls. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 1, pp. 31–34, January, 2006     

Prooxidant-antioxidant state of the organism during oxidative stress and correction of the L-arginine-NO system

The prooxidant-antioxidant balance in rats with oxidative stress was studied during correction of the L-arginine-NO system. Oxidative stress was induced by intravenous injection of E. coli lipopolysaccharide. Under conditions of oxidative stress the prooxidant-antioxidant imbalance was least pronounced during selective correction of the L-arginine-NO system. L-Arginine and nonselective NO synthase inhibitor had little protective effect. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 4, pp. 368–370, April, 2006     

Hormonal function of the adrenal glands in men and monkeys in hemoblastoses and during aging

Similar changes in the functioning of the adrenal glands (activation of cortisol synthesis due to a more complete utilization of its biochemical precursors and reduced formation of dehydroepiandrosterone and its sulfate fraction) are demonstrated in men and monkeys in hemoblastoses and during aging. It is assumed that being adaptive and nonspecific in nature, these changes lead to hormonal imbalance promoting the development of senile involution processes in patients and animals with severe chronic disease. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 8, pp. 207–210, August, 1997     

Cerebroprotective effects of diquertin and ascorbic acid

Electron microscopy and electrophysiological studies revealed pronounced structural and functional changes in the brain cortex in rats with experimental cerebral ischemia. Repeated administration of diquertin and ascorbic acid significantly attenuates ischemic damage induced by circulatory disturbances. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 130, No. 11, pp. 543–547, November, 2000     

Content of Steroid Hormones in the Blood and Adrenal Glands of Mice in the Dynamics of BCG- and SiO<Subscript>2</Subscript>-Induced Granulomatous Inflammation

Individual or combined administration of BCG vaccine and silicon dioxide to male mice induced a nonspecific stress response of the adrenal glands and gonads judging from changes in the concentration of blood cortisol and testosterone. The dynamics of cortisol concentration in the adrenal glands was similar, while changes in progesterone concentration were in antiphase to those in the blood. After combined administration of both inductors of granulomatous inflammation, changes in the concentrations of the studied hormones to a greater extent corresponded to their dynamics after injection of BCG. Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Suppl. 1, pp. 20-22, 2008     

Heart Rate Variability in Outbred White Rats upon Periodical α-Tocopherol Administration

Effect of α-tocopherol (vitamin E) periodical administration on heart rhythm regulation was investigated in outbred white rats. α-Tocopherol administration to males was followed by reduction of sympathetic neural influence on heart rhythm and also by the increase of the number of individuals with high activity of autonomic regulation loop. In female rats α-tocopherol administration modulates the activity of humoral control circuit and promotes heart rate reduction, however upon that the percent of females with high centralization of heart rate regulation was increased. Translated from Byulleten’ Experimental’noi Biologii i Meditsiny, Vol. 147, No 2, pp. 130–133, February, 2009     

Role of sex hormones in cardiovascular resistance to atropine in rats at rest and during stress

Castration of males and females reduces the sensitivity of cardiac chronotropic function to atropine and potentiates the vascular component in the reaction to atropine in females (during stress) and males (at rest and during stress). Our results show that estrogens and androgens increase the sensitivity of the cardiovascular system to cholinergic influences at rest and during stress. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 3, pp. 270–272, March, 2006     

Effect of β-casomorphin-7 on DNA synthesis in cell populations of newborn albino rats

We studied the effect of β-casomorphin-7 on DNA synthesis in cell populations of newborn albino rats. Intraperitoneal administration of a β-casein fragment heptapeptide β-casomorphin-7 (1 mg/kg, 1 or 5 injections) activated proliferative processes in the myocardium and ectodermal and endodermal epithelium of newborn rats. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 2, pp. 170–172, February, 2008