Modifications of anxiety-like behavior in prenatally stressed male offspring with imbalance of androgens.

Gonadal hormones have been well-known to affect brain regions known to be involved in the modulation of mood and affective-related behavior. Prenatal stress might alter hypothalamic-pituitary-gonadal axis, it could be a target for development of affective-related disorders in male offspring. The present study was designed to examine an anxiety-like behavior in the adult male offspring with low levels of endogenous androgens delivered from pregnant dams exposed to prenatal stress from gestation day 15 to gestation day 19. The non-stressed and prenatally stressed intact, gonadectomized (GDX) and GDX male offspring treated with oil solvent or testosterone propionate (TP, 0.5 mg/kg, s.c., 14 days, once daily) were used in all experiments. Anxiety-like behavior was assessed in the elevated plus maze (EPM) and the open field test (OFT), respectively. Also, testosterone levels in the blood serum were measured in all experimental groups of offspring. Prenatally stressed GDX offspring demonstrated a significant decrease for time spent into the open arms and increase for time spent into the closed arms as compared to the non-stressed offspring. Administration of TP to the prenatally stressed GDX offspring resulted in a more markedly decrease of the time spent into the open arms and significantly raised the time spent into the closed arms as compared to the non-stressed GDX offspring treated with TP, non-stressed/prenatally stressed GDX offspring. Prenatally stressed GDX offspring showed a significant increase of crossing, rearing, grooming and defecation as compared to the prenatally stressed control offspring. On the contrary, administration of TP to the prenatally stressed GDX offspring significantly decreased crossing behavior, frequency of rearing and grooming behavior as compared to the non-stressed GDX offspring treated with TP, non-stressed/prenatally stressed GDX offspring. Prenatally stressed GDX offspring demonstrated a significant decrease of testosterone levels as compared to the non-stressed/prenatally stressed intact offspring, as well as non-stressed GDX offspring. Administration of TP significantly increased testosterone levels when prenatally stressed GDX offspring were compared with the prenatally stressed intact offspring, non-stressed/prenatally stressed GDX offspring. Thus, the results of the study clearly suggest that gonadectomy and TP supplementation profoundly changed an anxiety-related behavior in prenatally stressed male offspring in the EPM. Our current findings suggest that androgen deficiency in the prenatally stressed male offspring produces the high anxiety level and induces a marked anxious-like state. TP supplementation provokes development of profoundly anxious-like state in the prenatally stressed male offspring, Furthermore, this is the first study to show anxiogenic-like effect of TP administration on anxiety-related states in prenatally stressed male offspring with androgen deficiency.

Effects of Chronic Vitamin D3 Hormone Administration on Anxiety-Like Behavior in Adult Female Rats after Long-Term Ovariectomy.

The present preclinical study was created to determine the therapeutic effects of vitamin D hormone treatment as an adjunctive therapy alone or in a combination with low dose of 17ß-estradiol (17ß-E2) on anxiety-like behavior in female rats with long-term absence of estrogen. Accordingly, the aim of the current study was to examine the effects of chronic cholecalciferol administration (1.0, 2.5 or 5.0 mg/kg subcutaneously, SC, once daily, for 14 days) on the anxiety-like state after long-term ovariectomy in female rats. Twelve weeks postovariectomy, cholecalciferol was administered to ovariectomized (OVX) rats and OVX rats treated with 17ß-E2 (0.5 µg/rat SC, once daily, for 14 days). Anxiety-like behavior was assessed in the elevated plus maze (EPM) and the light/dark test (LDT), and locomotor and grooming activities were tested in the open field test (OFT). Cholecalciferol at two doses of 1.0 and 2.5 mg/kg alone or in combination with 17ß-E2 produced anxiolytic-like effects in OVX rats as evidenced in the EPM and the LDT, as well as increased grooming activity in the OFT. Our results indicate that cholecalciferol, at two doses of 1.0 and 2.5 mg/kg, has a profound anxiolytic-like effects in the experimental rat model of long-term estrogen deficiency.

Postconditioning by mild hypoxic exposures reduces rat brain injury caused by severe hypoxia.

A potent neuroprotective effect of ischemic postconditioning has previously been described using cerebral artery occlusion but this is not a practical therapeutic option. The present study has been performed to determine whether postconditioning by mild episodes of hypobaric hypoxia (hypoxic postconditioning, HP) can reduce post-hypoxic brain injury in rats. Male Wistar rats were submitted to severe hypobaric hypoxia (180 Torr, 3 h) followed by HP (360 Torr, 2 h, 3 trials spaced at 24 h) starting either 3h (early HP) or 24 h (delayed HP) after severe hypoxia. The structural and functional brain injury was assessed by a complex of histological techniques, behavioral methods, and by testing the functions of the hypothalamic-pituitary-adrenal axis (HPA). It was found that early and delayed HP considerably attenuated post-hypoxic injury, reducing pyknosis, hyperchromatosis, and interstitial brain edema, as well as the rates of neuronal loss in hippocampus and neocortex. Delayed HP produced prominent anxiolytic effect on rat behavior, preventing development of post-hypoxic anxiety. Both modes of HP had beneficial effect on the functioning of HPA, but only delayed HP normalized completely the baseline HPA activity and its reactivity to stress. The results obtained demonstrate that postconditioning by using repetitive episodes of mild hypobaric hypoxia may provide a powerful neuroprotective procedure that can be easily adopted for clinical practice and recommended as a research tool for identification of endogenous mechanisms involved in post-ischemic neuroprotection.

Expression of glucocorticoid and mineralocorticoid receptors in hippocampus of rats exposed to various modes of hypobaric hypoxia: Putative role in hypoxic preconditioning.

Effects of mild (preconditioning) and severe injurious hypobaric hypoxia (SH), as well as of their combination on hippocampal expression of glucocorticoid (GR) and mineralocorticoid (MR) receptors and HPA axis activity have been examined in rats. As revealed by quantitative immunocytochemistry, three-trial exposure to mild hypoxia produced robust GR and MR overexpression located mainly in the neuronal nuclei in the dentate gyrus (DG) but only MR overexpression was observed in the CA1. SH induced sharp reduction of MR levels and enhanced GR expression in the CA1, suggesting that the unbalance of GR and MR observed might be at the bottom of the extensive neuronal loss seen in this area in response to SH. Contrastingly, SH in tolerant (preconditioned) rats failed to imbalance GR and MR expression in CA1 and up-regulated GR levels in DG. Radioimmunoassay of serum corticosterone showed that both preconditioning hypoxia itself and SH in tolerant rats produced moderate activation of HPA axis followed by its proper inactivation. In the non-preconditioned rats, HPA axis response to SH was impaired. Taken together, these novel results suggest that modifications of the hippocampal expression of GR and MR produced by preconditioning may contribute to the molecular and neuroendocrine mechanisms of tolerance to severe hypoxic stress.

Postnatal ontogeny of the glucocorticoid receptor in the hippocampus.

Corticosteroid hormones are important intrinsic factors that not only mediate the response to stress but also largely contribute to the main physiological processes. The biological actions of these steroids involve, first of all, the activation of specific receptors, namely mineralocorticoid (MR) and glucocorticoid (GR) receptors. These two receptor types govern a flexible and well-balanced mechanism that leads to the often opposing changes in the cell. The hippocampus is the central part of the extrahypothalamic feedback loop in the control of the hypothalamic-pituitary-adrenal (HPA) axis activity. The coexpression of both MR and GR in the hippocampus serves a coordinated response to corticosteroids in the hippocampal neurons, thereby mediating the neuronal excitability, stress response, and behavioral adaptation. Each receptor type reveals distinct ontogenetic pattern over the postnatal period. This review addresses the issues relating to postnatal development of the HPA axis and especially the hippocampal expression of the GR proteins in intact and prenatally stressed rats.

Involvement of the hypothalamic-pituitary-adrenal axis in the antidepressant-like effects of mild hypoxic preconditioning in rats.

The preconditioning (PC) by using mild intermittent hypobaric hypoxia (PC) increases a resistance of the brain to severe hypoxia/ischemia and various stresses. Recently, potent antidepressant-like effects of PC have been described in animal models of depression. In the present study, the impact of PC on the activity and feedback regulation of the hypothalamic-pituitary-adrenal axis (HPA) impaired in depression has been studied in the model of shock-induced depression in rats. PC completely prevented depressive-like behavior (54% reduction in ambulance, 59% reduction in rearing in the open field, 654% increase of the anxiety level in the elevated plus maze), the HPA hyperactivity and the impairment of HPA feedback regulation that appeared in response to the inescapable footshock. Not affecting basal HPA activity, PC remarkably enhanced the HPA reactivity to stresses and substantially up-regulated the expression of glucocorticoid receptors in the ventral hippocampus following footshock that apparently contributes to the mechanisms responsible for the antidepressant-like action of PC.

Antidepressant-like effects of mild hypoxia preconditioning in the learned helplessness model in rats.

The effects of preconditioning using mild repetitive hypobaric hypoxia (360 Torr for 2 h each of 3 days) have been studied in the learned helplessness model of depression in rats. Male Wistar rats displayed persistent depressive symptoms (depressive-like behaviour in open field, increased anxiety levels in elevated plus maze, ahedonia, elevated plasma glucocorticoids and impaired dexamethasone test) following the exposure to unpredictable and inescapable footshock in the learned helplessness paradigm. Antidepressant treatment (ludiomil, 5 mg/kg i.p.) augmented the development of the depressive state. The hypoxic preconditioning had a clear antidepressive action returning the behavioural and hormonal parameters to the control values and was equally effective in terms of our study as the antidepressant. The findings suggest hypoxic preconditioning as an effective tool for the prophylaxis of post-stress affective pathologies in humans.

Expression of glucocorticoid receptors in the hippocampal region of the rat brain during postnatal development.

Circulating glucocorticoids, of which their concentration is largely under the control of the hypothalamic-pituitary adrenal (HPA) axis, acting through the glucocorticoid receptors (GR) regulate a large variety of pivotal functions of the organism such as growth, development, immune- and stress-response. The main mechanism of regulation of the HPA axis activity is via negative feedback at all levels of the HPA axis itself as well as at the extra-hypothalamic level, a central part of which is the hippocampus. During neonatal development, the HPA axis of rats undergoes a period of hyporesponsiveness (SHRP)-when most stress stimuli fail to induce stress-response. Here, we describe the pattern of GR proteins expression in the hippocampal area of the rat brain during postnatal development and in adulthood. We demonstrated that the GR protein, of which its expression level is gradually enhanced in the hippocampus during postnatal life, exists in three different molecular sized forms. A larger molecular form was expressed at rather high levels at all studied time periods. A second smaller variant of GR was transiently expressed during the first one and a half weeks that corresponds with SHRP and then appeared again only in the adulthood. By the end of SHRP on PD 13, third smallest protein form of GR started to be detected in the hippocampal area. Thus, it remains to be disclosed in the nearest future, how the hippocampal GR isoforms may be involved in regulation of the neonatal HPA axis hyporesponsiveness as well as in functions of this system during the ensuing period of the brain maturation.