Estradiol abolishes autologous down regulation of glucocorticoid receptors in brain

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

The hippocampus is a brain structure known to play a central role in cognitive function (namely learning and memory) as well as mood regulation and affective behaviors due in part to its ability to undergo structural and functional changes in response to intrinsic and extrinsic stimuli. While structural changes are achieved through modulation of hippocampal neurogenesis as well as alterations in dendritic morphology and spine remodeling, functional (i.e., synaptic) changes can be noted through the strengthening (i.e., long-term potentiation) or weakening (i.e., long-term depression) of the synapses. While age, hormone homeostasis, and levels of physical activity are some of the factors known to module these forms of hippocampal plasticity, the exact mechanisms through which these factors interact with each other at a given moment in time are not completely understood. It is well known that hormonal levels vary throughout the lifespan of an individual and it is also known that physical exercise can impact hormonal homeostasis. Thus, it is reasonable to speculate that hormone modulation might be one of the various mechanisms through which physical exercise differently impacts hippocampal plasticity throughout distinct periods of an individual's life. The present review summarizes the potential relationship between physical exercise and different types of hormones (namely sex, metabolic, and stress hormones) and how this relationship may mediate the effects of physical activity during three distinct life periods, adolescence, adulthood, and senescence. Overall, the vast majority of studies support a beneficial role of exercise in maintaining hippocampal hormonal levels and consequently, hippocampal plasticity, cognition, and mood regulation.

Prevention of Osteoporosis in the Ovariectomized Rat by Oral Administration of a Nutraceutical Combination That Stimulates Nitric Oxide Production

Osteoporosis represents an imbalance between bone formation and bone resorption. As a result of low estrogen levels, it is markedly prevalent during menopause, thus making such patients susceptible to fractures. Both bone formation and resorption are modulated by nitric oxide (NO). Currently, there are no risk-free pharmaceutical prevention therapies for osteoporosis. COMB-4, a nutraceutical combination of Paullinia cupana, Muira puama, ginger, and L-citrulline, known to activate the NO-cGMP pathway, was reported to accelerate fracture healing in the rat. To determine whether COMB-4 could be effective in preventing menopausal osteoporosis, it was compared to estradiol (E2) in an ovariectomized (OVX) rat osteoporosis model. Nine-month-old female Sprague Dawley rats were divided into SHAM, OVX, OVX+E2, and OVX+COMB-4. After 100 days of treatment, bone mineral density (BMD) and bone mineral content (BMC) were measured by DXA scan. TRAP staining was performed in the femur and lumbar vertebrae. TRACP 5b and osteocalcin levels were assayed in the serum. MC3T3-E1 cells were differentiated into osteoblasts and treated with COMB-4 for one week in order to evaluate calcium deposition by Alizarin staining, cGMP production by ELISA, and upregulation of the nitric oxide synthase (NOS) enzymes by RT-PCR. OVX resulted in a decrease in BMD, BMC, and serum osteocalcin and an increase in serum TRACP 5b. Except for an increase in BMC with COMB-4, both E2 and COMB-4 reverted all bone and serum markers, as well as the number of osteoclasts in the vertebrae, to SHAM levels. Incubation of MC3T3-E1 cells with COMB-4 demonstrated an increase in the three NOS isoforms, cGMP, and calcium deposition. COMB-4 increased BMD in OVX rats by inhibiting bone resorption and increasing calcium deposition presumably via activation of the NO-cGMP pathway. It remains to be determined whether COMB-4 could be a potential nutraceutical therapy for the prevention of premenopausal bone loss.

Prolonged ovarian hormone deprivation alters the effects of 17β-estradiol on microRNA expression in the aged female rat hypothalamus

Administration of 17β-estradiol (E₂) has beneficial effects on cognitive function in peri- but not post-menopausal women, yet the molecular mechanisms underlying age-related changes in E₂ action remain unclear. We propose that there is a biological switch in E₂ action that occurs coincident with age and length of time after ovarian hormone depletion, and we hypothesized that age-dependent regulation of microRNAs (miRNAs) could be the molecular basis for that switch. Previously we showed that miRNAs are regulated by E₂ in young compared to aged female rats. Here we tested whether increasing lengths of ovarian hormone deprivation in aged females altered E₂ regulation of these mature miRNAs. In addition, we determined where along the miRNA biogenesis pathway E₂ exerted its effects. Our results showed that age and increased lengths of ovarian hormone deprivation abolished the ability of E₂ to regulate mature miRNA expression in the brain. Further, we show that E₂ acted at specific points along the miRNA biogenesis pathway.

Pharmacotherapy with 17β-estradiol and progesterone prevents development of mouse experimental autoimmune encephalomyelitis

BACKGROUND

Pregnant women with multiple sclerosis (MS) show disease remission in the third trimester concomitant with high circulating levels of sex steroids. Rodent experimental autoimmune encephalomyelitis (EAE) is an accepted model for MS. Previous studies have shown that monotherapy with estrogens or progesterone exert beneficial effects on EAE. The aim of the present study was to determine if estrogen and progesterone cotherapy of C57BL/6 female mice provided substantial protection from EAE.

METHODS

A group of mice received single pellets of progesterone (100 mg) and 17 β-estradiol (2.5 mg) subcutaneously 1 week before EAE induction, whereas another group were untreated before EAE induction. On day 16 we compared the two EAE groups and control mice in terms of clinical scores, spinal cord demyelination, expression of myelin basic protein and proteolipid protein, macrophage cell infiltration, neuronal expression of brain-derived neurotrophic factor mRNA and protein, and the number of glial fribrillary acidic protein (GFAP)-immunopositive astrocytes.

RESULTS

Clinical signs of EAE were substantially attenuated by estrogen and progesterone treatment. Steroid cotherapy prevented spinal cord demyelination, infiltration of inflammatory cells and GFAP+ astrogliocytes to a great extent. In motoneurons, expression of BDNF mRNA and protein was highly stimulated, indicating concomitant beneficial effects of the steroid on neuronal and glial cells.

CONCLUSIONS

Cotherapy with estrogen and progesterone inhibits the development of major neurochemical abnormalities and clinical signs of EAE. We suggest that a combination of neuroprotective, promyelinating and immuno-suppressive mechanisms are involved in these beneficial effects.

Actions and interactions of estradiol and glucocorticoids in cognition and the brain: Implications for aging women

Menopause involves dramatic declines in estradiol production and levels. Importantly, estradiol and the class of stress hormones known as glucocorticoids exert countervailing effects throughout the body, with estradiol exerting positive effects on the brain and cognition, glucocorticoids exerting negative effects on the brain and cognition, and estradiol able to mitigate negative effects of glucocorticoids. Although the effects of these hormones in isolation have been extensively studied, the effects of estradiol on the stress response and the neuroprotection offered against glucocorticoid exposure in humans are less well known. Here we review evidence suggesting that estradiol-related protection against glucocorticoids mitigates stress-induced interference with cognitive processes. Animal and human research indicates that estradiol-related mitigation of glucocorticoid damage and interference is one benefit of estradiol supplementation during peri-menopause or soon after menopause. The evidence for estradiol-related protection against glucocorticoids suggests that maintaining estradiol levels in post-menopausal women could protect them from stress-induced declines in neural and cognitive integrity.

Sex differences in the HPA axis

The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development. Despite this, many studies use male subjects exclusively, while fewer reports involve females or provide direct sex comparisons. The purpose of this article is to present sex comparisons in the functional and molecular aspects of the HPA axis, through various phases of activity, including basal, acute stress, and chronic stress conditions. The HPA axis in females initiates more rapidly and produces a greater output of stress hormones. This review focuses on the interactions between the gonadal hormone system and the HPA axis as the key mediators of these sex differences, whereby androgens increase and estrogens decrease HPA activity in adulthood. In addition to the effects of gonadal hormones on the adult response, morphological impacts of hormone exposure during development are also involved in mediating sex differences. Additional systems impinging on the HPA axis that contribute to sex differences include the monoamine neurotransmitters norepinephrine and serotonin. Diverse signals originating from the brain and periphery are integrated to determine the level of HPA axis activity, and these signals are, in many cases, sex-specific.

Effects of maternal separation on the dietary preference and behavioral satiety sequence in rats

This study investigated the effects of maternal separation on the feeding behavior of rats. A maternal separation model was used on postnatal day 1 (PND1), forming the following groups: in the maternal separation (MS) group, pups were separated from their mothers each day from PND1 to PND14, whereas in the control (C) group pups were kept with their mothers. Subgroups were formed to study the effects of light and darkness: control with dark and light exposure, female and male (CF and CM), and maternal separation with dark and light exposure, female and male (SDF, SDM, SLF and SLM). Female rats had higher caloric intake relative to body weight compared with male controls in the dark period only (CF=23.3±0.5 v. CM=18.2±0.7, P<0.001). Macronutrient feeding preferences were observed, with male rats exhibiting higher caloric intake from a protein diet as compared with female rats (CF=4.1±0.7, n=8 v. CM=7.0±0.5, n=8, P<0.05) and satiety development was not interrupted. Female rats had a higher adrenal weight as compared with male rats independently of experimental groups and exhibited a higher concentration of serum triglycerides (n=8, P<0.001). The study indicates possible phenotypic adjustments in the structure of feeding behavior promoted by maternal separation, especially in the dark cycle. The dissociation between the mother's presence and milk intake probably induces adjustments in feeding behavior during adulthood.

Sex differences in the neurobiology of drug addiction

Epidemiological data demonstrate that while women report lower rates of drug use than men, the number of current drug users and abusers who are women continues to increase. In addition women progress through the phases of addiction differently than men; women transition from casual drug use to addiction faster, are more reactive to stimuli that trigger relapse, and have higher rates of relapse then men. Sex differences in physiological and psychological responses to drugs of abuse are well documented and it is well established that estrogen effects on dopamine (DA) systems are largely responsible for these sex differences. However, the downstream mechanisms that result from interactions between estrogen and the effects of drugs of abuse on the DA system are just beginning to be explored. Here we review the basic neurocircuitry which underlies reward and addiction; highlighting the neuroadaptive changes that occur in the mesolimbic dopamine reward and anti-reward/stress pathways. We propose that sex differences in addiction are due to sex differences in the neural systems which mediate positive and negative reinforcement and that these differences are modulated by ovarian hormones. This forms a neurobehavioral basis for the search for the molecular and cellular underpinnings that uniquely guide motivational behaviors and make women more vulnerable to developing and sustaining addiction than men.

Dietary fructose-related adiposity and glucocorticoid receptor function in visceral adipose tissue of female rats

PURPOSE

Excessive fructose intake coincides with the growing rate of obesity and metabolic syndrome, with women being more prone to these disorders than men. Findings that detrimental effects of fructose might be mediated by glucocorticoid regeneration in adipose tissue only indirectly implicated glucocorticoid receptor (GR) in the phenomenon. The aim of the present study was to elucidate whether fructose overconsumption induces derangements in GR expression and function that might be associated with fructose-induced adiposity in females.

METHODS

We examined effects of fructose-enriched diet on GR expression and function in visceral adipose tissue of female rats. Additionally, we analyzed the expression of genes involved in glucocorticoid prereceptor metabolism [11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and hexose-6-phosphate dehydrogenase], lipolysis (hormone-sensitive lipase) and lipogenesis (sterol regulatory element binding protein 1 and peroxisomal proliferator-activated receptor γ).

RESULTS

Fructose-fed rats had elevated energy intake that resulted in visceral adiposity, as indicated by increased visceral adipose tissue mass and its share in the whole-body weight. GR hormone binding capacity and affinity, as well as the expression of GR gene at both mRNA and protein levels were reduced in visceral adipose tissue of the rats on fructose diet. The glucocorticoid prereceptor metabolism was stimulated, as evidenced by elevated tissue corticosterone, while the key regulators of lipolysis and lipogenesis remained unaffected by fructose diet.

CONCLUSIONS

The results suggest that the 11βHSD1-mediated elevation of intracellular corticosterone may induce GR downregulation, which may be associated with failure of GR to stimulate lipolysis in fructose-fed female rats.

Progesterone down-regulates spinal cord inflammatory mediators and increases myelination in experimental autoimmune encephalomyelitis

In mice with experimental autoimmune encephalomyelitis (EAE) pretreatment with progesterone improves clinical signs and decreases the loss of myelin basic protein (MBP) and proteolipid protein (PLP) measured by immunohistochemistry and in situ hybridization. Presently, we analyzed if progesterone effects in the spinal cord of EAE mice involved the decreased transcription of local inflammatory mediators and the increased transcription of myelin proteins and myelin transcription factors. C57Bl/6 female mice were divided into controls, EAE and EAE receiving progesterone (100mg implant) 7 days before EAE induction. Tissues were collected on day 17 post-immunization. Real time PCR technology demonstrated that progesterone blocked the EAE-induced increase of the proinflammatory mediators tumor necrosis factor alpha (TNFα) and its receptor TNFR1, the microglial marker CD11b and toll-like receptor 4 (TLR4) mRNAs, and increased mRNA expression of PLP and MBP, the myelin transcription factors NKx2.2 and Olig1 and enhanced CC1+oligodendrocyte density respect of untreated EAE mice. Immunocytochemistry demonstrated decreased Iba1+microglial cells. Confocal microscopy demonstrated that TNFα colocalized with glial-fibrillary acidic protein+astrocytes and OX-42+microglial cells. Therefore, progesterone treatment improved the clinical signs of EAE, decreased inflammatory glial reactivity and increased myelination. Data suggest that progesterone neuroprotection involves the modulation of transcriptional events in the spinal cord of EAE mice.

Progesterone attenuates demyelination and microglial reaction in the lysolecithin-injured spinal cord

Progesterone treatment of mice with experimental autoimmune encephalomyelitis has shown beneficial effects in the spinal cord according to enhanced clinical, myelin and neuronal-related parameters. In the present work, we report progesterone effects in a model of primary demyelination induced by the intraspinal injection of lysophospatidylcholine (LPC). C57Bl6 adult male mice remained steroid-untreated or received a single 100 mg progesterone implant, which increased circulating steroid levels to those of mouse pregnancy. Seven days afterwards mice received a single injection of 1% LPC into the dorsal funiculus of the spinal cord. A week after, anesthetized mice were perfused and paraffin embedded sections of the spinal cord stained for total myelin using Luxol Fast Blue (LFB) histochemistry, for myelin basic protein (MBP) immunohistochemistry and for determination of OX-42+ microglia/macrophages. Cryostat sections were also prepared and stained for oligodendrocyte precursors (NG2+ cells) and mature oligodendrocytes (CC1+ cells). A third batch of spinal cords was prepared for analysis of the microglial marker CD11b mRNA using qPCR. Results showed that progesterone pretreatment of LPC-injected mice decreased by 50% the area of demyelination, evaluated by either LFB staining or MBP immunostaining, increased the density of NG2+ cells and of mature, CC1+ oligodendrocytes and decreased the number of OX-42+ cells, respect of steroid-untreated LPC mice. CD11b mRNA was hyperexpressed in LPC-treated mice, but significantly reduced in LPC-mice receiving progesterone. These results indicated that progesterone antagonized LPC injury, an effect involving (a) increased myelination; (b) stimulation of oligodendrocyte precursors and mature oligodendrocytes, and (c) attenuation of the microglial/macrophage response. Thus, use of a focal demyelination model suggests that progesterone exerts promyelinating and anti-inflammatory effects at the spinal cord level.

Acute stress may induce ovulation in women

BACKGROUND

This study aims to gather information either supporting or rejecting the hypothesis that acute stress may induce ovulation in women. The formulation of this hypothesis is based on 2 facts: 1) estrogen-primed postmenopausal or ovariectomized women display an adrenal-progesterone-induced ovulatory-like luteinizing hormone (LH) surge in response to exogenous adrenocorticotropic hormone (ACTH) administration; and 2) women display multiple follicular waves during an interovulatory interval, and likely during pregnancy and lactation. Thus, acute stress may induce ovulation in women displaying appropriate serum levels of estradiol and one or more follicles large enough to respond to a non-midcycle LH surge.

METHODS

A literature search using the PubMed database was performed to identify articles up to January 2010 focusing mainly on women as well as on rats and rhesus monkeys as animal models of interaction between the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes.

RESULTS

Whereas the HPA axis exhibits positive responses in practically all phases of the ovarian cycle, acute-stress-induced release of LH is found under relatively high plasma levels of estradiol. However, there are studies suggesting that several types of acute stress may exert different effects on pituitary LH release and the steroid environment may modulate in a different way (inhibiting or stimulating) the pattern of response of the HPG axis elicited by acute stressors.

CONCLUSION

Women may be induced to ovulate at any point of the menstrual cycle or even during periods of amenorrhea associated with pregnancy and lactation if exposed to an appropriate acute stressor under a right estradiol environment.

Stage dependent effects of progesterone on motoneurons and glial cells of wobbler mouse spinal cord degeneration

In the Wobbler mouse, a mutation in the Vps54 gene is accompanied by motoneuron degeneration and astrogliosis in the cervical spinal cord. Previous work has shown that these abnormalities are greatly attenuated by progesterone treatment of clinically afflicted Wobblers. However, whether progesterone is effective at all disease stages has not yet been tested. The present work used genotyped (wr/wr) Wobbler mice at three periods of the disease: early progressive (1-2 months), established (5-8 months) or late stages (12 months) and age-matched wildtype controls (NFR/NFR), half of which were implanted with a progesterone pellet (20 mg) for 18 days. In untreated Wobblers, degenerating vacuolated motoneurons were initially abundant, experienced a slight reduction at the established stage and dramatically diminished during the late period. In motoneurons, the cholinergic marker choline acetyltransferase (ChAT) was reduced at all stages of the Wobbler disease, whereas hyperexpression of the growth-associated protein (GAP43) mRNA preferentially occurred at the early progressive and established stages. Progesterone therapy significantly reduced motoneuron vacuolation, enhanced ChAT immunoreactive perikarya and reduced the hyperexpression of GAP43 during the early progressive and established stages. At all stage periods, untreated Wobblers showed high density of glial fibrillary acidic protein (GFAP)+ astrocytes and decreased number of glutamine synthase (GS) immunostained cells. Progesterone treatment down-regulated GFAP+ astrocytes and up-regulated GS+ cell number. These data reinforced the usefulness of progesterone to improve motoneuron and glial cell abnormalities of Wobbler mice and further showed that therapeutic benefit seems more effective at the early progressive and established periods, rather than on advance stages of spinal cord neurodegeneration.

Effects of progesterone on oligodendrocyte progenitors, oligodendrocyte transcription factors, and myelin proteins following spinal cord injury

Progesterone is emerging as a myelinizing factor for central nervous system injury. Successful remyelination requires proliferation and differentiation of oligodendrocyte precursor cells (OPC) into myelinating oligodendrocytes, but this process is incomplete following injury. To study progesterone actions on remyelination, we administered progesterone (16 mg/kg/day) to rats with complete spinal cord injury. Rats were euthanized 3 or 21 days after steroid treatment. Short progesterone treatment (a) increased the number of OPC without effect on the injury-induced reduction of mature oligodendrocytes, (b) increased mRNA and protein expression for the myelin basic protein (MBP) without effects on proteolipid protein (PLP) or myelin oligodendrocyte glycoprotein (MOG), and (c) increased the mRNA for Olig2 and Nkx2.2 transcription factors involved in specification and differentiation of the oligodendrocyte lineage. Furthermore, long progesterone treatment (a) reduced OPC with a concomitant increase of oligodendrocytes; (b) promoted differentiation of cells that incorporated bromodeoxyuridine, early after injury, into mature oligodendrocytes; (c) increased mRNA and protein expression of PLP without effects on MBP or MOG; and (d) increased mRNA for the Olig1 transcription factor involved in myelin repair. These results suggest that early progesterone treatment enhanced the density of OPC and induced their differentiation into mature oligodendrocytes by increasing the expression of Olig2 and Nkx2.2. Twenty-one days after injury, progesterone favors remyelination by increasing Olig1 (involved in repair of demyelinated lesions), PLP expression, and enhancing oligodendrocytes maturation. Thus, progesterone effects on oligodendrogenesis and myelin proteins may constitute fundamental steps for repairing traumatic injury inflicted to the spinal cord.

Estrogen impairs glucocorticoid dependent negative feedback on the hypothalamic-pituitary-adrenal axis via estrogen receptor alpha within the hypothalamus

Numerous studies have established a link between individuals with affective disorders and a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, most notably characterized by a reduced sensitivity to glucocorticoid negative (-) feedback. Furthermore there is a sex difference in the etiology of mood disorders with incidence in females being two to three times that of males, an association that may be a result of the influence of estradiol (E2) on HPA axis function. In these studies, we have examined the effect of E2 on glucocorticoid-mediated HPA axis (-) feedback during both the diurnal peak and the stress-induced rise in corticosterone (CORT). Young adult female Sprague-Dawley (SD) rats were ovariectomized (OVX) and 1 week later treated subcutaneous (s.c.) with oil or estradiol benzoate (EB) for 4 days. On the 4th day of treatment, animals were injected with a single dose of dexamethasone (DEX), or vehicle. EB treatment significantly increased the evening elevation in CORT and the stress-induced rise in CORT. In contrast, DEX treatment reduced the diurnal and stress induced rise in CORT and adrenocorticotropic hormone (ACTH), and this reduction was not apparent following co-treatment with EB. To determine a potential site of E2's action, female SD rats were OVX and 1 week later, wax pellets containing E2, the estrogen receptor beta (ERbeta) agonist diarylpropionitrile (DPN), or the estrogen receptor alpha (ERalpha) agonist propylpyrazoletriol (PPT), was implanted bilaterally and dorsal to the paraventricular nucleus of the hypothalamus (PVN). Seven days later, animals were injected s.c. with a single dose of DEX, or vehicle to test for glucocorticoid-dependent (-) feedback. Results show that E2 and PPT increased, while DPN decreased the diurnal peak and stress-induced CORT and ACTH levels as compared to controls. Furthermore, E2 and PPT impaired the ability of DEX to inhibit both the diurnal and the stress-induced rise in CORT and ACTH, whereas DPN had no effect. Neuronal activation was measured by c-fos mRNA expression within the PVN following restraint. E2 and PPT increased c-fos mRNA, and impaired the normal DEX suppression of neuronal activation in the PVN. Taken together, these data indicate that estradiol causes a dysregulation of HPA axis (-) feedback as evidenced by the inability of DEX to suppress diurnal and stress-induced CORT and ACTH secretion. Additionally, the ability of E2 to inhibit glucocorticoid (-) feedback occurs specifically via ERalpha acting at the level of the PVN.

Effects of progesterone in the spinal cord of a mouse model of multiple sclerosis

The spinal cord is a target of progesterone (PROG), as demonstrated by the expression of intracellular and membrane PROG receptors and by its myelinating and neuroprotective effects in trauma and neurodegeneration. Here we studied PROG effects in mice with experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis characterized by demyelination and immune cell infiltration in the spinal cord. Female C57BL/6 mice were immunized with a myelin oligodendrocyte glycoprotein peptide (MOG(40-54)). One week before EAE induction, mice received single pellets of PROG weighing either 20 or 100 mg or remained free of steroid treatment. On average, mice developed clinical signs of EAE 9-10 days following MOG administration. The spinal cord white matter of EAE mice showed inflammatory cell infiltration and circumscribed demyelinating areas, demonstrated by reductions of luxol fast blue (LFB) staining, myelin basic protein (MBP) and proteolipid protein (PLP) immunoreactivity (IR) and PLP mRNA expression. In motoneurons, EAE reduced the expression of the alpha 3 subunit of Na,K-ATPase mRNA. In contrast, EAE mice receiving PROG showed less inflammatory cell infiltration, recovery of myelin proteins and normal grain density of neuronal Na,K-ATPase mRNA. Clinically, PROG produced a moderate delay of disease onset and reduced the clinical scores. Thus, PROG attenuated disease severity, and reduced the inflammatory response and the occurrence of demyelination in the spinal cord during the acute phase of EAE.

Progesterone modulates brain-derived neurotrophic factor and choline acetyltransferase in degenerating Wobbler motoneurons

Progesterone (PROG) shows neuroprotective effects in nervous system diseases. The Wobbler mouse, a model of motoneuron degeneration, suffers a mutation of the Vsp154 gene on chromosome 11 leading to motoneuron vacuolation and astrocytosis of the spinal cord. Previous work has demonstrated beneficial effects of PROG in the Wobbler mouse. As an extension of this work, we now studied steroid effects on neuronal brain-derived neurotrophic factor (BDNF) mRNA and protein, on choline acetyltransferase (ChAT) immunoreactivity (IR) and activity in the spinal cord, and on recovery of muscle atrophy. Wobbler mice received implants of PROG pellets (20 mg) at 6 and 10 weeks of age and were killed at 14 weeks. In situ hybridization for BDNF mRNA demonstrated that grain density in large (>600 microm2) and medium size (<600 microm2) ventral horn neurons was decreased in untreated Wobblers, whereas PROG treatment increased BDNF mRNA in both neuronal types. PROG also induced a subcellular redistribution of BDNF protein, which in controls and steroid-naive Wobblers showed a predominant perinuclear and nucleolar location, whereas after PROG treatment, it was detected in cytoplasmic aggregates. ChAT activity was reduced by 55.3% in muscles of untreated Wobbler mice, whereas a significant increment was obtained after PROG treatment. Wobblers also showed reduced number of ChAT positive motoneurons, but this number was restored to normal by PROG. Finally, the pronounced biceps atrophy of steroid-naive Wobbler mice was slightly but significantly increased by PROG-treatment. Considering the important role played by neurotrophins on neuronal function, changes in BDNF might be part of the PROG activated-pathways to provide neuroprotection and re-establish neurotransmission and neuromuscular function in this degeneration model.

Hippocampal neuropathology of diabetes mellitus is relieved by estrogen treatment

1. A recently recognized complication of uncontrolled diabetes mellitus is the encephalopathy involving, among other regions, the hippocampus. Since estrogens bring neuroprotection in cases of brain injury and degenerative diseases, we have studied if estradiol (E2) administration counteracts some hippocampal abnormalities of streptozotocin (STZ)-diabetic adult mice. 2. We first report the ability of E2 to modulate neurogenesis in the dentate gyrus (DG) and subventricular zone (SVZ) of diabetic mice. Using bromodeoxyuridine (BrdU) to label newly generated cells, a strong reduction in cell proliferation was obtained in DG and SVZ of mice sacrificed 20 days after STZ administration. The reduction was completely relieved by 10 days of E2 pellet implantation, which increased 30-fold the circulating E2 levels. 3. Diabetic mice also showed abnormal expression of astrocyte markers in hippocampus. Thus, increased number of GFAP(+) cells, indicative of astrogliosis, and increased number of apolipoprotein-E (Apo-E)(+) astrocytes, a marker of ongoing neuronal dysfunction, was found in stratum radiatum below the CA1 hippocampal subfield of diabetic mice. Both parameters were reverted to normal by the E2 regime that upregulated cell proliferation. 4. The studies demonstrated that hippocampal neuropathology of uncontrolled diabetes is a reversible condition and sensitive to estrogen treatment. Studies in animal models may open up new venues for understanding the beneficial role of steroid hormones in diabetic encephalopathy.

Progesterone increases the expression of myelin basic protein and the number of cells showing NG2 immunostaining in the lesioned spinal cord

It is now widely accepted that progesterone (PROG) brings neuroprotection in lesions of the peripheral and central nervous system. Spinal cord trauma leads to neuronal degeneration, astrogliosis, demyelination, and proliferation of oligodendrocyte-precursor cells (OPCs). In this work, we studied the effects of PROG on myelin-related parameters in rats with complete spinal cord transection (TRX). To this end, sham-operated controls and rats with TRX at thoracic level T10 received vehicle or PROG (4 mg/kg/day) during 3 days. Three variables were measured in the lumbar L4 region below the lesion: (1) expression of myelin basic protein (MBP) at the protein and mRNA levels; (2) density of NG2-immunopositive cells as markers for OPCs; and (3) number of cells immunopositive for RIP, an antibody staining mature oligodendrocytes. TRX decreased MBP immunostaining in the corticospinal tract (CST) and dorsal ascending tract (DAT) but not the ventral funiculus (VF). NG2+ cells, which were detected in low number in controls, increased after TRX in the gray and white matter. RIP-positive cell number, however, remained unchanged. PROG treatment of rats with TRX enhanced the expression of MBP protein and mRNA in CST and DAT, but not VF and highly stimulated the number of cells showing NG2 immunostaining over untreated lesioned rats. Instead, density of RIP positive cells was similar in the PROG-treated and untreated lesioned groups. We propose that PROG effects on expression of MBP and the number of NG2 immunopositive cells may contribute to neuroprotection, as they go in parallel with previous results showing enhanced biochemical and morphological parameters of motoneurons of animals with TRX receiving PROG treatment.

Molecular endocrinology and physiology of the aging central nervous system

Aging is associated with a progressive decline in physical and cognitive functions. The impact of age-dependent endocrine changes regulated by the central nervous system on the dynamics of neuronal behavior, neurodegeneration, cognition, biological rhythms, sexual behavior, and metabolism are reviewed. We also briefly review how functional deficits associated with increases in glucocorticoids and cytokines and declining production of sex steroids, GH, and IGF are likely exacerbated by age-dependent molecular misreading and alterations in components of signal transduction pathways and transcription factors.

Effects of injury and progesterone treatment on progesterone receptor and progesterone binding protein 25-Dx expression in the rat spinal cord

Progesterone provides neuroprotection after spinal cord injury, but the molecular mechanisms involved in this effect are not completely understood. In this work, expression of two binding proteins for progesterone was studied in intact and injured rat spinal cord: the classical intracellular progesterone receptor (PR) and 25-Dx, a recently discovered progesterone membrane binding site. RT-PCR was employed to determine their relative mRNA levels, whereas cellular localization and relative protein levels were investigated by immunocytochemistry. We observed that spinal cord PR mRNA was not up-regulated by estrogen in contrast to what is observed in many brain areas and in the uterus, but was abundant as it amounted to a third of that measured in the estradiol-stimulated uterus. In male rats with complete spinal cord transection, levels of PR mRNA were significantly decreased, while those of 25-Dx mRNA remained unchanged with respect to control animals. When spinal cord-injured animals received progesterone treatment during 72 h, PR mRNA levels were not affected and remained low, whereas 25-Dx mRNA levels were significantly increased. Immunostaining of PR showed its intracellular localization in both neurons and glial cells, whereas 25-Dx immunoreactivity was localized to cell membranes of dorsal horn and central canal neurons. As the two binding proteins for progesterone differ with respect to their response to lesion, their regulation by progesterone, their cellular and subcellular localizations, their functions may differ under normal and pathological conditions. These observations point to a novel and potentially important role of the progesterone binding protein 25-Dx after injury of the nervous system and suggest that the neuroprotective effects of progesterone may not necessarily be mediated by the classical progesterone receptor but may involve distinct membrane binding sites.

Progesterone up-regulates neuronal brain-derived neurotrophic factor expression in the injured spinal cord

Progesterone (PROG) provides neuroprotection to the injured central and peripheral nervous system. These effects may be due to regulation of myelin synthesis in glial cells and also to direct actions on neuronal function. Recent studies point to neurotrophins as possible mediators of hormone action. Here, we show that the expression of brain-derived neurotrophic factor (BDNF) at both the mRNA and protein levels was increased by PROG treatment in ventral horn motoneurons from rats with spinal cord injury (SCI). Semiquantitative in situ hybridization revealed that SCI reduced BDNF mRNA levels by 50% in spinal motoneurons (control: 53.5+/-7.5 grains/mm(2) vs. SCI: 27.5+/-1.2, P<0.05), while PROG administration to injured rats (4 mg/kg/day during 3 days, s.c.) elicited a three-fold increase in grain density (SCI+PROG: 77.8+/-8.3 grains/mm(2), P<0.001 vs. SCI). In addition, PROG enhanced BDNF immunoreactivity in motoneurons of the lesioned spinal cord. Analysis of the frequency distribution of immunoreactive densities (chi(2): 812.73, P<0.0001) showed that 70% of SCI+PROG motoneurons scored as dark stained whereas only 6% of neurons in the SCI group belonged to this density score category (P<0.001). PROG also prevented the lesion-induced chromatolytic degeneration of spinal cord motoneurons as determined by Nissl staining. In the normal intact spinal cord, PROG significantly increased BDNF inmunoreactivity in ventral horn neurons, without changes in mRNA levels. Our findings suggest that PROG enhancement of endogenous neuronal BDNF could provide a trophic environment within the lesioned spinal cord and might be part of the PROG activated-pathways to provide neuroprotection.

Gonadal and adrenal effects on the glucocorticoid receptor in the rat hippocampus, with special reference to regulation by estrogen from an immunohistochemical view-point

Focusing on the hippocampal CA1 region, effects of peripheral gonadal and adrenal steroids on the glucocorticoid receptor (GR) were immunohistochemically evaluated in male and female adult rat brains after adrenalectomy (ADX), gonadectomy (GDX), and administration of estradiol (E2) and/or corticosterone (CS). In ADXed male rats, the hippocampal nuclear GR decreased and turned back to the cytoplasm, whereas in females, nuclear localization persisted even after ADX. In GDX+ADXed female rats, the GR was dispersedly translocated from the nucleus to the cytoplasm as well as in GDX+ADXed males. The dispersed cytoplasmic GR was again translocated into the nucleus by administration of CS. In addition, administration of a small dose of E2 for 4-13 days was found to sufficiently recover the nuclear location of GR in GDX+ADXed rat brains, whereas medium-to-large doses could not do this. Also, a longer administration more strongly enhances the nuclear GR location and expression. The present study provided strong immunohistochemical evidence that the sexually dimorphic effects of ADX on hippocampal GR are attributable to gonadal hormones, and that E2 is implicated in the effects in inversely-dose- and directly-duration-dependent manner. Taken together, intriguing gonadal and adrenal crosstalk is considered to play some important role in regulating hippocampal GR morphology and to have a possibly crucial influence on stress-related disorders such as depression.

Increased astrocyte reactivity in the hippocampus of murine models of type 1 diabetes: the nonobese diabetic (NOD) and streptozotocin-treated mice

Diabetes can be associated with cerebral dysfunction in humans and animal models of the disease. Moreover, brain anomalies and alterations of the neuroendocrine system are present in type 1 diabetes (T1D) animals, such as the spontaneous nonobese diabetic (NOD) mouse model and/or the pharmacological streptozotocin (STZ)-induced model. Because of the prevalent role of astrocytes in cerebral glucose metabolism and their intimate connection with neurones, we investigated hippocampal astrocyte alterations in prediabetic and diabetic NOD mice and STZ-treated diabetic mice. The number and cell area related to the glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes were quantified in the stratum radiatum region of the hippocampus by computerized image analysis in prediabetic (2, 4 and 8 weeks of age) and diabetic (16-week-old) NOD female mice, age and sex-matched lymphocyte-deficient NODscid and C57BL/6 control mice and, finally, STZ-induced diabetic and vehicle-treated nondiabetic 16-week-old C57BL/6 female mice. Astrocyte number was higher early in life in prediabetic NOD and NODscid mice than in controls, when transient hyperinsulinemia and low glycemia were found in these strains. The number and cell area of GFAP(+) cells further increased after the onset of diabetes in NOD mice. Similarly, in STZ-treated diabetic mice, the number of GFAP(+) cells and cell area were higher than in vehicle-treated mice. In conclusion, astrocyte changes present in genetic and pharmacological models of T1D appear to reflect an adaptive process to alterations of glucose homeostasis.

Cellular basis for progesterone neuroprotection in the injured spinal cord

Progesterone (PROG) exerts beneficial and neuroprotective effects in the injured central and peripheral nervous system. In the present work, we examine PROG effects on three measures of neuronal function under negative regulation (choline acetyltransferase [ChAT] and Na,K-ATPase) or stimulated (growth-associated protein [GAP-43]) after acute spinal cord transection injury in rats. As expected, spinal cord injury reduced ChAT immunostaining intensity of ventral horn neurons. A 3-day course of intensive PROG treatment of transected rats restored ChAT immunoreactivity, as assessed by frequency histograms that recorded shifts from predominantly light neuronal staining to medium, dark or intense staining typical of control rats. Transection also reduced the expression of the mRNA for the alpha3 catalytic and beta1 regulatory subunits of neuronal Na,K-ATPase, whereas PROG treatment restored both subunit mRNA to normal levels. Additionally, the upregulation observed for GAP-43 mRNA in ventral horn neurons in spinal cord-transected rats, was further enhanced by PROG administration. In no case did PROG modify ChAT immunoreactivity, Na,K-ATPase subunit mRNA or GAP-43 mRNA in control, sham-operated rats. Further, the PROG-mediated effects on these three markers were observed in large, presumably Lamina IX motoneurons, as well as in smaller neurons measuring approximately <500 micro2. Overall, the stimulatory effects of PROG on ChAT appears to replenish acetylcholine, with its stimulatory effects on Na,K-ATPase seems capable of restoring membrane potential, ion transport and nutrient uptake. PROG effects on GAP-43 also appear to accelerate reparative responses to injury. As the cellular basis for PROG neuroprotection becomes better understood it may prove of therapeutic benefit to spinal cord injury patients.

Increased vasopressin and adrenocorticotropin responses to stress in the midluteal phase of the menstrual cycle

Accumulating evidence indicates that gonadal steroids modulate functioning of the hypothalamic-pituitary-adrenal (HPA) axis, which has been closely linked to the pathophysiology of anxiety and depression. However, the effect of the natural menstrual cycle on HPA axis responsivity to stress has not been clearly described. In nine healthy women, metabolic and hormonal responses to treadmill exercise stress during the early follicular phase of the menstrual cycle, when gonadal steroid levels are low, were compared with responses in the midluteal phase of the cycle, when both progesterone and estrogen levels are relatively high. Exercise intensity was gradually increased over 20 min to reach 90% of each subject's maximal oxygen consumption during the final 5 min of exercise. Basal plasma lactate, glucose, ACTH, vasopressin, oxytocin, and cortisol levels were similar in the two cycle phases. However, in response to exercise stress, women in the midluteal phase had enhanced ACTH (P < 0.0001), vasopressin (P < 0.01), and glucose (P < 0.001) secretion. These findings suggest that relatively low levels of gonadal steroids during the early follicular phase of the menstrual cycle provide protection from the impact of stress on the HPA axis.

Progestin regulation of galanin and prolactin gene expression in oestrogen-induced pituitary tumours

Galanin is a peptide widely distributed in the hypothalamic-pituitary axis. In the female rat pituitary, galanin is mainly present in lactotrophs, where it regulates their secretion and proliferation. Galanin expression is increased in oestrogen-induced prolactinomas, and it has been proposed that oestrogen effects on lactotroph function and proliferation could be mediated by galanin. Previous studies from our laboratory demonstrated that the synthetic progestin levonorgestrel antagonizes pituitary tumorigenesis of rats given oestrogen, reducing the number of proliferating cells and increasing cell death by nonapoptotic mechanism(s). To elucidate the role of galanin in levonorgestrel effects on the tumours, we examined galanin and prolactin mRNA and peptide expression in prolactinomas of rats receiving the progestin. Levonorgestrel reduced the pituitary weight and serum prolactin concentrations in oestrogen-treated rats. Galanin mRNA expression (determined by in situ hybridization), and the number of galanin expressing cells (determined by immunocytochemistry) were also reduced by the progestin in tumour-bearing rats. However, neither prolactin mRNA content, nor the number of prolactin-expressing cells, were modified by levonorgestrel treatment of oestrogen-receiving rats. The present study suggests that levonorgestrel controls pituitary growth by diminishing galanin expression. In contrast, changes in serum prolactin concentration seem to be more related to the reduction in tumour size, since the reduction in galanin expression was not large enough to regulate prolactin mRNA expression or the percentage of lactotrophs.

Diabetes increases the expression of hypothalamic neuropeptides in a spontaneous model of type I diabetes, the nonobese diabetic (NOD) mouse

1. Synthesis of oxytocin (OT) and arginine-vasopressin (AVP) is increased in induced models of Type I diabetes, such as the streptozotocin model. However, these parameters have not yet been evaluated in spontaneous models, such as the nonobese diabetic mouse (NOD). Therefore, we studied in the magnocellular cells of the paraventricular nucleus (PVN) of nondiabetic and diabetic 16-week-old female NOD mice and control C57B1/6 mice, the immunocytochemistry of OT and AVP peptides and their mRNA expression, using nonisotopic in situ hybridization (ISH). 2. In nondiabetic and diabetic NOD female mice, the number of OT- and AVP-immunoreactive cells were similar to those of the controls, whereas immunoreaction intensity was significantly higher for both peptides in diabetic NOD as compared with nondiabetic NOD and control C57B1/6 mice. 3. ISH analysis showed that the number of OT mRNA-containing cells was in the same range in the three groups, whereas higher number of AVP mRNA expressing cells was found in diabetic NOD mice. However, the intensity of hybridization signal was also higher for both OT and AVP mRNA in the diabetic group as compared with nondiabetic NOD and control mice. 4. Blood chemistry demonstrated that haematrocrit, total plasma proteins, urea, sodium, and potassium were within normal limits in diabetic mice. Thus, NOD mice were neither hypernatremic nor dehydrated. 5. We suggest that upregulation of OT and AVP reflects a high-stress condition in the NOD mice. Diabetes may affect neuropeptide-producing cells of the PVN, with the increased AVP and OT playing a deleterious role on the outcome of the disease.

Modulation of NADPH-diaphorase and glial fibrillary acidic protein by progesterone in astrocytes from normal and injured rat spinal cord

Progesterone (P4) can be synthesized in both central and peripheral nervous system (PNS) and exerts trophic effects in the PNS. To study its potential effects in the spinal cord, we investigated P4 modulation (4 mg/kg/day for 3 days) of two proteins responding to injury: NADPH-diaphorase, an enzyme with nitric oxide synthase activity, and glial fibrillary acidic protein (GFAP), a marker of astrocyte reactivity. The proteins were studied at three levels of the spinal cord from rats with total transection (TRX) at T10: above (T5 level), below (L1 level) and caudal to the lesion (L3 level). Equivalent regions were dissected in controls. The number and area of NADPH-diaphorase active or GFAP immunoreactive astrocytes/0.1 mm(2) in white matter (lateral funiculus) or gray matter (Lamina IX) was measured by computerized image analysis. In controls, P4 increased the number of GFAP-immunoreactive astrocytes in gray and white matter at all levels of the spinal cord, while astrocyte area also increased in white matter throughout and in gray matter at the T5 region. In control rats P4 did not change NADPH-diaphorase activity. In rats with TRX and not receiving hormone, a general up-regulation of the number and area of GFAP-positive astrocytes was found at all levels of the spinal cord. In rats with TRX, P4 did not change the already high GFAP-expression. In the TRX group, instead, P4 increased the number and area of NADPH-diaphorase active astrocytes in white and gray matter immediately above and below, but not caudal to the lesion. Thus, the response of the two proteins to P4 was conditioned by environmental factors, in that NADPH-diaphorase activity was hormonally modulated in astrocytes reacting to trauma, whereas up-regulation of GFAP by P4 was produced in resting astrocytes from non-injured animals.

Dopamine function in obsessive compulsive disorder: cortisol response to acute apomorphine stimulation

Central dopaminergic dysfunction has been suggested to be involved in the pathogenesis of obsessive compulsive disorder (OCD). In 15 patients with OCD and in 15 age-sex matched controls we evaluated the dopamine (DA) function by measuring the cortisol (CORT) responses to stimulation with the DA agonist apomorphine (APO). The CORT response to acute saline administration was also measured, to exclude the existence of a pathology of the circadian secretion of the hormone which could obscure the significance of the CORT response to APO stimulation. Basal levels of CORT were the same in patients and controls, but the values after saline administration were significantly higher in patients than in controls. APO stimulation-induced CORT rises were significantly higher in patients than in controls, but when the data after APO were corrected for those after saline, there were no significant difference between the two groups of subjects. Our data suggest that there are no alterations of the central dopaminergic function connected with the regulation of the hypothalamo-pituitary-adrenal axis in OCD.

In vitro differences between astrocytes of control and wobbler mice spinal cord

The Wobbler mouse, a model of amyotrophic lateral sclerosis (ALS), presents motorneuron degeneration and pronounced astrogliosis in the spinal cord. We have studied factors controlling astrocyte proliferation in cultures derived from Wobbler and control mice spinal cord. Basal rate of [3H]thymidine incorporation was 15 times lower in Wobbler astrocytes. While in control cultured cells interleukin-1alpha (IL-1) and corticosterone (CORT) significantly increased proliferation, both agents were inactive in Wobbler astrocytes. The lack of response to CORT was not due to the absence of glucocorticoid receptors, because similar receptor amounts were found in Wobbler and control astrocytes. In contrast to IL-1 and CORT, transforming growth factor-beta1 (TGF-beta1) substantially increased proliferation of Wobbler astrocytes but not of control cells. Differences in response to TGF-beta1 were also obtained by measuring glial fibrillary acidic protein (GFAP) immunoreaction intensity, which was substantially higher in Wobbler astrocytes. Thus, abnormal responses to different mitogens characterized Wobbler astrocytes in culture. We suggest that TGF-beta1 may play a role in the reactive gliosis and GFAP hyperexpression found in the degenerating spinal cord of this model of ALS.

Glucocorticoid regulation of motoneuronal parameters in rats with spinal cord injury

1. Glucocorticoids exert beneficial effects after acute CNS injury in humans and experimental animals. To elucidate potential mechanisms of glucocorticoid action in the lesioned spinal cord, we have studied if treatment with dexamethasone (DEX) modulated the neurotrophin binding receptor p75 (p75NTR) and choline acetyltransferase (ChAT), a marker of neuronal functional viability. 2. Rats with a sham operation or with spinal cord transection at the thoracic level received vehicle or DEX several times postlesion and were sacrificed 48 hr after surgery. The lumbar region caudal to the lesion was processed for p75NTR and ChAT immunoreactivity (IR) using quantitative densitometric analysis. 3. We observed that p75NTR-IR was absent from ventral horn motoneurons of sham-operated rats, in contrast to strong staining of neuronal perikaryon in TRX rats. Administration of DEX to TRX rats had no effect on the number of neuronal cell bodies expressing p75NTR-IR but significantly increased the number and length of immunostained neuronal processes. 4. Furthermore, spinal cord transection reduced ChAT immunostaining of motoneurons by 50%, whereas DEX treatment reverted this pattern to cells with a strong immunoreaction intensity in perikaryon and cell processes. 5. It is hypothesized that increased expression of p75NTR in cell processes and of ChAT in motoneurons may be part of a mechanism by which glucocorticoids afford neuroprotection, in addition to their known antiinflammatory effects.

Changes of hypothalamic and plasma vasopressin in rats with deoxycorticosterone-acetate induced salt appetite

Mineralocorticoids play a predominant role in development of salt appetite and hypertension. Since vasoactive peptides could mediate the central effects of mineralocorticoids, we evaluated changes of immunoreactive (IR) arginine vasopressin (AVP) in the paraventricular (PVN) and supraoptic (SON) hypothalamic nucleus during DOCA-induced salt appetite. In one model, rats having free access to water and 3% NaCl during 9 (prehypertensive stage) or 21 days (hypertensive stage) received DOCA (s.c., 10 mg/rat/in alternate days). A decrease in the IR cell area, number of IR cells and staining intensity was obtained in magnocellular PVN of rats treated during 9 days. After 21 days IR cell area and number of cells in the PVN also decreased, but staining intensity of remaining cells was normal. The same parameters were unchanged in the SON. In another model, animals treated with DOCA during 9 days had only access to 3% NaCl or water. The IR cell area in PVN and SON significantly increased in mineralocorticoid-treated and control animals, both drinking 3% NaCl. Staining intensity (PVN and SON) and number of IR cells (PVN) also augmented in DOCA-treated animals drinking salt respect of a group drinking water. Plasma AVP in rats treated with DOCA and offered salt and water, exhibited a 2-2.5 fold increase at the time of salt appetite induction. Plasma AVP was substantially higher in rats drinking salt only, while the highest levels were present in salt-drinking DOCA-treated rats. Thus, peptide depletion in the PVN may be due to increased release, because reduced levels of hypothalamic and posterior pituitary AVP were measured in this model. In rats drinking salt only the substantial increase of IR AVP in the PVN and SON, may be due to dehydration and hyperosmosis. Because DOCA-salt treated rats showed higher AVP levels in the PVN compared to untreated rats drinking salt only, it is possible that DOCA sensitized PVN cells to increase AVP production. The results suggest the vasopressinergic system could mediate some central functions of mineralocorticoids.

Estrogen supplementation attenuates glucocorticoid and catecholamine responses to mental stress in perimenopausal women

Estrogens are reported to provide protection against the development of cardiovascular disease in women, but the mechanisms underlying these effects are not well defined. We hypothesized that estrogen might affect the hormonal responses to stress. We therefore studied cortisol, ACTH, epinephrine, norepinephrine, and norepinephrine spillover and hemodynamic responses to a 10-min mental arithmetic test in 12 perimenopausal women randomized to 8 weeks of estrogen supplementation (estradiol valerate, 2 mg daily; n = 7) or placebo (n = 5). Total body and forearm norepinephrine spillover were measured by radiotracer methodology. After supplementation with estradiol, the increases in both systolic and diastolic blood pressure in response to mental stress were reduced, and cortisol, ACTH, plasma epinephrine and norepinephrine, and total body norepinephrine spillover responses to stress were significantly attenuated (P < 0.05 in each case). Forearm norepinephrine spillover was unchanged by estrogen, and there was no change in any of the responses after placebo. We conclude that estrogen supplementation in perimenopausal women attenuates blood pressure, glucocorticoid, and catecholamine responses to psychological stress.

The 21-aminosteroid U-74389F attenuates hyperexpression of GAP-43 and NADPH-diaphorase in the spinal cord of wobbler mouse, a model for amyotrophic lateral sclerosis

The wobbler mouse suffers an autosomal recessive mutation producing severe neurodegeneration and astrogliosis in spinal cord. It has been considered a model for amyotrophic lateral sclerosis. We have studied in these animals the expression of two proteins, the growth-associated protein (GAP-43) and the NADPH-diaphorase, the nitric oxide synthesizing enzyme, employing immunocytochemistry and histochemistry. We found higher expression of GAP-43 immunoreactivity in dorsal horn, Lamina X, corticospinal tract and ventral horn motoneurons in wobbler mice compared to controls. Weak NADPH-diaphorase activity was present in control motoneurons, in contrast to intense labeling of the wobbler group. No differences in diaphorase activity was measured in the rest of the spinal cord between control and mutant mice. A group of animals received subcutaneously for 4 days a 50 mg pellet of U-74389F, a glucocorticoid-derived 21-aminosteroid with antioxidant properties but without glucocorticoid activity. U-74389F slightly attenuated GAP-43 immunostaining in dorsal regions of the spinal cord from wobblers but not in controls. However, in motoneurons of wobbler mice number of GAP-43 immunopositive neurons, cell processes and reaction intensity were reduced by U-74389F. The aminosteroid reduced by 50% motoneuron NADPH-diaphorase activity. Hyperexpression of GAP-43 immunoreactivity in wobbler mice may represent an exaggerated neuronal response to advancing degeneration or muscle denervation. It may also be linked to increased nitric oxide levels. U-74389F may stop neurodegeneration and/or increase muscle trophism and stop oxidative stress, consequently GAP-43 hyperexpression was attenuated. Wobbler mice may be important models to evaluate the use of antioxidant steroid therapy with a view to its use in human motoneuron disease.

Effects of estrogen and estrous cycle on glucocorticoid and catecholamine responses to stress in sheep

There have been relatively few studies of the effects of estrogen on hormonal responses to stress. We therefore studied changes in ACTH, cortisol, norepinephrine (NE), and epinephrine (Epi) after stress induced by a barking dog (audiovisual stressor) and insulin-induced hypoglycemia (metabolic stressor) in ovariectomized sheep treated with estradiol or placebo and in intact sheep in the follicular and luteal phases of the estrous cycle. Both stressors produced acute increases in ACTH, cortisol, Epi, and NE. A high physiological dose of estradiol significantly reduced the ACTH and cortisol responses to both stressors but did not affect Epi and NE responses. Plasma ACTH and cortisol responses to both stressors and Epi and NE responses to insulin were lower in the follicular than in the luteal phase, but catecholamine responses to the audiovisual stressor did not change during the estrous cycle. We conclude that in sheep, estrogen attenuates glucocorticoid responses to stress and that hormonal changes during the estrous cycle affect glucocorticoid responses to both metabolic and audiovisual stressors and catecholamine responses to a metabolic stressor.

Regulation of gene expression by corticoid hormones in the brain and spinal cord

Glucocorticoids (GC) and mineralocorticoids (MC) have profound regulatory effects upon the central nervous system (CNS). Hormonal regulation affects several molecules essential to CNS function. First, evidences are presented that mRNA expression of the alpha3 and beta1-subunits of the Na,K-ATPase are increased by GC and physiological doses of MC in a region-dependent manner. Instead, high MC doses reduce the beta1 isoform and enzyme activity in amygdaloid and hypothalamic nuclei, an effect which may be related to MC control of salt appetite. The alpha3-subunit mRNA of the Na,K-ATPase is also stimulated by GC in motoneurons of the injured spinal cord, suggesting a role for the enzyme in GC neuroprotection. Second, we provide evidences for hormonal effects on the expression of mRNA for the neuropeptide arginine vasopressin (AVP). Our data show that GC inhibition of AVP mRNA levels in the paraventricular nucleus is sex-hormone dependent. This sexual dimorphism may explain sex differences in the hypothalamic-pituitary-adrenal axis function between female and male rats. Third, steroid effects on the astrocyte marker glial fibrillary acidic protein (GFAP) points to a complex regulatory mechanism. In an animal model of neurodegeneration (the Wobbler mouse) showing pronounced astrogliosis of the spinal cord, in vivo GC treatment down-regulated GFAP immunoreactivity, whereas the membrane-active steroid antioxidant U-74389F up-regulated this protein. It is likely that variations in GFAP protein expression affect spinal cord neurodegeneration in Wobbler mice. Fourth, an interaction between neurotrophins and GC is shown in the injured rat spinal cord. In this model, intensive GC treatment increases immunoreactive low affinity nerve growth factor (NGF) receptor in motoneuron processes. Because GC also increases immunoreactive NGF, this mechanism would support trophism and regeneration in damaged tissues. In conclusion, evidences show that some molecules regulated by adrenal steroids in neurons and glial cells are not only involved in physiological control, but additionally, may play important roles in neuropathology.

Sex difference in glucocorticoid regulation of vasopressin mRNA in the paraventricular hypothalamic nucleus

1. Arginine vasopressin (AVP) is synthesized in specific brain regions including the magnocellular and parvocellular divisions of the paraventricular nucleus (PVN). Whereas magnocellular AVP responds to osmotic stimuli and functions mainly--although not exclusively--as an antidiuretic hormone, that produced in the parvocellular region controls the hypothalamus-pituitary-adrenal (HPA) axis, in conjunction with CRF. 2. In view of the reported sex differences in control of the HPA axis, we studied if these also pertain to AVP mRNA in the PVN of ovariectomized-estrogenized female rats and male rats determined by in situ hybridization. AVP mRNA was measured in intact rats, adrenalectomized (ADX) rats and ADX receiving dexamethasone (DEX) of both sexes. 3. Computerized autoradiography showed that in both sexes, AVP mRNA levels in the parvocellular division of the PVN increased after adrenalectomy and decreased following DEX. However, the reduction by DEX was more pronounced in female rats. No changes were found for the magnocellular region. Grain counting analysis of the medial-medial (MMP) and medial-lateral (MLP) subdivisions of the parvocellular region showed that the average number of grains per cell area in the MMP region of adrenally intact female rats was higher than that in males. However, in females there was no clear-cut effect of adrenalectomy on AVP mRNA levels, although the reduction after DEX treatment was again greater than that in male rats. Frequency histograms constructed by plotting the number of cells vs the number of grains per area substantiated the enhanced glucocorticoid negative control of AVP mRNA in the MMP and MLP of female rats. 4. The results indicated a sexual dimorphism in the glucocorticoid-dependent plasticity of AVP mRNA levels in the PVN. Because AVP mRNA expression differs between sexes under basal levels, after adrenalectomy, and after DEX treatment, these plastic changes may differentially condition the response to stress. Taking into consideration that stress and AVP may play a role in neurogenic hypertension, the possibility of sexual dimorphisms in AVP control may be important to assess the role of sex hormones in stress and steroid-derived hypertension.

Interaction of corticosterone and gonadal steroids on lipid deposition in the female rat

The present study was designed to evaluate the interaction of corticosterone (CORT) and female gonadal steroids on energy balance and lipid metabolism. To this end, a 2 x 4 factorial experiment was carried out in which two cohorts of rats differing in their ovary status [OV status: intact (INT) and ovariectomy (OVX)] were each divided into four groups defined by their CORT status [CORT status: nonadrenalectomized (non-ADX), ADX without CORT replacement (placebo subcutaneous pellet), ADX with low-dose CORT replacement, and ADX with high-dose CORT replacement]. After 3 wk of treatment and a 12-h fast, rats were killed and their carcasses analyzed for energy (lipid and protein) content. In addition, indexes of endogenous triglyceride (TRIG) production (liver TRIG content), transport into plasma (triglyceridemia), and incorporation into fat stores [lipoprotein lipase (LPL) activity in adipose tissue (AT)] were assessed. OV and CORT status interacted on body weight gain, total energy, and fat gains. The interactions arose from the fact that the twofold increase in these variables brought on by OVX was abolished by ADX and restored by CORT replacement. Although in ADX groups there was a dose-related restoration of total energy and fat gain by CORT replacement in both INT and OVX cohorts, the impact thereupon of OVX observed in the non-ADX group reappeared only in ADX animals receiving the high dose of CORT. Protein gain was increased by OVX solely in non-ADX rats, whereas the high dose of CORT prevented any net protein gain independently of the OV status. Consistent with treatment effects on total body fat gain, OVX resulted in an increase in liver TRIG content, AT weight, AT LPL activity, and plasma insulin. All these effects of OVX were abolished by ADX and restored by the high dose of CORT. Plasma TRIG were unaffected by OV status but were highly responsive to CORT status. All treatment effects were highly correlated with cumulative food intake. This study shows that the presence of CORT is required for OVX to exert its action on global energy balance and the concomitant, closely integrated adaptations of lipid metabolism.