Chronic administration of androgens with actions at estrogen receptor beta have anti-anxiety and cognitive-enhancing effects in male rats

Apoptosis in hippocampal tissue induced by oxidative stress in testosterone deprived male rats

The testosterone decline is one of the potential causes of oxidative stress-induced anxiety and depressive behaviors, and cognitive impairment induces irreversible neuronal damage, which is not clearly understood. The orchidectomized rat model was used; the hippocampal neurons and anxiety behavior were analyzed. Adult male albino rats were divided into control and orchidectomy (ORX) groups, orchidectomy (ORX + T), and normal (Cont + T) groups. Testosterone propionate was used as a testosterone supplement. The anxiety and depressive-like behavior observed in ORX animals in the open field (OF) and elevated plus-maze experiments were effectively overturned in the ORX + T group. Studies on isolated hippocampus showed reduced antioxidant enzymes (SOD, CAT, and glutathione (GSH) compounds), increased lipid peroxidation (LPO), elevated caspase3, and reduced anti-apoptotic protein Bcl-2, and increased apoptotic nuclei in TUNEL staining of the hippocampus in the ORX rats. These observations indicate free radical-mediated neural damage. Testosterone presence promoted the antioxidant defense system and restored normal pyramidal neuron morphology in ORX + T. This study confirms that testosterone is indispensable in the normal adult hippocampus and deficiency seems to be a potential risk factor for neurodegenerative disorders. Besides, androgen appears to be a possible therapeutic strategy for treating depression/neurodegenerative diseases in aging men.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Bisphenol-A inhibits improvement of testosterone in anxiety- and depression-like behaviors in gonadectomied male mice

Bisphenol-A (BPA) is a well-known environmental endocrine disruptor. Developmental exposure to BPA affected a variety of behaviors in multiple model organisms. Our recent study found that exposure to BPA during adulthood aggravated anxiety- and depression-like states in male mice but not in females. In this study, 11-w-old gonadectomied (GDX) male mice daily received subcutaneous injections of testosterone propionate (TP, 0.5 mg/kg), TP and BPA (0.04, 0.4, or 4 mg/kg), or vehicle for 45 days. BPA (0.4 or 4 mg/kg) did not affect the elevated plus maze task of GDX mice but shortened the time on open arms and decreased the frequency of head dips of sham and TP-GDX mice. In forced swim task, BPA prolonged the total time of immobility of both sham and TP-GDX mice but not GDX mice. In addition, BPA reduced the levels of T in the serum and the brain of sham and TP-GDX mice. Western blot analysis further showed that BPA reduced the levels of androgen receptor (AR) and GABA(A)α2 receptor of the hippocampus and the amygdala in sham and inhibited the rescue of TP in these proteins levels of GDX mice. Meanwhile, BPA decreased the level of phospho-ERK1/2 in these two brain regions of sham and TP-GDX mice. These results suggest that long-term exposure to BPA inhibited TP-improved anxiety- and depression-like behaviors in GDX male mice. The down-regulated levels of GABA(A)α2 receptor and AR and an inhibited activity of ERK1/2 pathway in the hippocampus and the amygdala may be involved in these process.

The Effects of Bisphenol A Exposure at Different Developmental Time Points in an Androgen-Sensitive Neuromuscular System in Male Rats

The industrial plasticizer bisphenol A (BPA) is a ubiquitous endocrine disruptor to which the general human population is routinely exposed. Although BPA is well known as an estrogenic mimic, there have been some suggestions that this compound may also alter activity at the androgen receptor. To determine whether BPA does have antiandrogenic properties, we evaluated BPA effects in the spinal nucleus of the bulbocavernosus and dorsolateral nucleus, sexually dimorphic groups of motor neurons in the lumbar spinal cord that are critically dependent on androgens for survival and maintenance, as well as the monomorphic retrodorsolateral nucleus. In experiment 1, we administered varying concentrations of BPA to juvenile rats pre- and postnatally and examined both the number and size of motor neurons in adulthood. In experiment 2, different doses of BPA were given to adult rats for 28 days, after which the soma size of motor neurons were measured. Although no effect of BPA on neural survival or soma size was noted after perinatal BPA exposure, BPA exposure did result in a decrease in soma size in all motor neuron pools after chronic exposure in adulthood. These findings are discussed with regard to putative antiandrogenic effects of BPA; we argue that BPA is not antiandrogenic but is acting through nonandrogen receptor-dependent mechanisms.

Perinatal exposure to di-(2-ethylhexyl) phthalate affects anxiety- and depression-like behaviors in mice

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental endocrine disrupter. The present study investigated the effect of DEHP on emotional behavior of mice following perinatal exposure (10, 50, and 200 mg kg(-1) d(-1)) from gestation day 7 through postnatal day 21. The results showed that, in pubertal males (6-w-old), DEHP decreased the time spent in the open arms and the number of entries into them in elevated plus maze and decreased the time in the mirrored chamber and in the light-box; in pubertal females, DEHP decreased the time spent in the open arms and the number of entries into them, suggesting that DEHP exposure made a anxiogenic effect in pubertal offspring regardless of sex. While DEHP effect on anxiety of adult (12-w-old) displayed sex differences, with decreased time spent in the open arms in the adult females. Perinatal exposure to DEPH significantly extended the time of immobility in forced swim task of pubertal offspring and adulthood regardless of sex. Furthermore, DEHP down-regulated the expressions of androgen receptor (AR) in pubertal male hippocampus and of estrogen receptor (ER) β in pubertal female and adult hippocampus of both sexes and inhibited the phosphorylation of ERK1/2 of hippocampus in pubertal mice and adult males. These results suggest that exposure to DEHP early in life affected the anxiety- and depressive-like behaviors of pubertal offspring and even adult. The disruption of gonadal hormones' modulation of behaviors due to down-regulation of AR or ERβ in the hippocampus may be associated with the aggravated anxiety- and depression-like status induced by DEHP.

Sex-specific effects of long-term exposure to bisphenol-A on anxiety- and depression-like behaviors in adult mice

Humans are routinely exposed to low levels of bisphenol A (BPA), an environmental endocrine disruptor, which is widely used in the production of polycarbonate plastics. The effects of perinatal exposure to BPA have been shown to affect various aspects of social behaviors such as anxiety and depression in adult offspring. Because sex hormones play a critical role in neurobehavior in adulthood, it is possible that long-term exposure to BPA has widespread effects on these emotional behaviors in adulthood. In the present study, adult mice were exposed to BPA at dosages of 0.04, 0.4, 4, 40 mg kg(-1)d(-1) for 12 weeks. A behavioral assay was performed using the open field test (OFT), mirrored maze, the elevated plus maze (EPM), and the forced swim task. The results showed that, after exposure to BPA at 0.4-40 mg kg(-1)d(-1), the number of open arm entries and the time spent in them in the elevated plus maze task were reduced in males but increased in females, and thus eliminating or reversing sex differences in these behaviors. BPA at 0.04-40 mg kg(-1)d(-1) increased the immobility of male mice in the forced swimming test. Furthermore, BPA (0.4-40 mg kg(-1)d(-1)) significantly decreased brain level of testosterone in males, but no significant influence was found in serum and the brain levels of estradiol in females. Western blot analysis further indicated that BPA at 0.4, 4, or 40 mg kg(-1)d(-1) significantly down-regulated the protein level of estrogen receptor β (ERβ) in the hippocampus of the adult males but not females, and inhibited the protein level of GABA(A)α2 receptor in hippocampus of males but promoted that of females. These results suggest that long-term exposure to BPA sex specifically affects anxiety- and depression-like behaviors in adult mice. Changes in the levels of GABA(A)α2 receptor and ERβ proteins of hippocampus might be associated with BPA-induced changes in these emotional behaviors.

Nonsteroidal selective androgen receptor modulators and selective estrogen receptor β agonists moderate cognitive deficits and amyloid-β levels in a mouse model of Alzheimer's disease

Decreases of the sex steroids, testosterone and estrogen, are associated with increased risk of Alzheimer's disease. Testosterone and estrogen supplementation improves cognitive deficits in animal models of Alzheimer's disease. Sex hormones play a role in the regulation of amyloid-β via induction of the amyloid-β degrading enzymes neprilysin and insulin-degrading enzyme. To mimic the effect of dihydrotestosterone (DHT), we administered a selective androgen receptor agonist, ACP-105, alone and in combination with the selective estrogen receptor β (ERβ) agonist AC-186 to male gonadectomized triple transgenic mice. We assessed long-term spatial memory in the Morris water maze, spontaneous locomotion, and anxiety-like behavior in the open field and in the elevated plus maze. We found that ACP-105 given alone decreases anxiety-like behavior. Furthermore, when ACP-105 is administered in combination with AC-186, they increase the amyloid-β degrading enzymes neprilysin and insulin-degrading enzyme and decrease amyloid-β levels in the brain as well as improve cognition. Interestingly, the androgen receptor level in the brain was increased by chronic treatment with the same combination treatment, ACP-105 and AC-186, not seen with DHT or ACP-105 alone. Based on these results, the beneficial effect of the selective ERβ agonist as a potential therapeutic for Alzheimer's disease warrants further investigation.

The role of testicular hormones and luteinizing hormone in spatial memory in adult male rats

Attempts to determine the influence of testicular hormones on learning and memory in males have yielded contradictory results. The present studies examined whether testicular hormones are important for maximal levels of spatial memory in young adult male rats. To minimize any effect of stress, we used the Object Location Task which is a spatial working memory task that does not involve food or water deprivation or aversive stimuli for motivation. In Experiment 1 sham gonadectomized male rats demonstrated robust spatial memory, but gonadectomized males showed diminished spatial memory. In Experiment 2 subcutaneous testosterone (T) capsules restored spatial memory performance in gonadectomized male rats, while rats with blank capsules demonstrated compromised spatial memory. In Experiment 3, gonadectomized male rats implanted with blank capsules again showed compromised spatial memory, while those with T, dihydrotestosterone (DHT), or estradiol (E) capsules demonstrated robust spatial memory, indicating that T's effects may be mediated by its conversion to E or to DHT. Gonadectomized male rats injected with Antide, a gonadotropin-releasing hormone receptor antagonist which lowers luteinizing hormone levels, also demonstrated spatial memory, comparable to that shown by T-, E-, or DHT-treated males. These data indicate that testicular androgens are important for maximal levels of spatial working memory in male rats, that testosterone may be converted to E and/or DHT to exert its effects, and that some of the effects of these steroid hormones may occur via negative feedback effects on LH.

Testosterone reduces cumulative burying in female Wistar rats with minimal participation of estradiol

Testosterone exerts anxiolytic effects, but the participation of its aromatase metabolic product estradiol is controversial. Therefore, we used the defensive burying paradigm in female Wistar rats to explore testosterone's (1.0 mg/rat, s.c.) interactions with picrotoxin (a noncompetitive gamma-aminobutyric acid-A receptor [GABA(A)] antagonist; 1.0 mg/kg, i.p.), formestane (an aromatase inhibitor; 3.0 mg/rat, s.c.), and tamoxifen (an estrogen receptor-beta antagonist; 1.0 mg/kg, s.c.). Serum levels of testosterone, estradiol, and progesterone were determined in the same rats. Burying latency and locomotion did not significantly change. Systemic testosterone administration enhanced serum testosterone and estradiol levels and reduced defensive burying. This reduction in total burying was blocked by pretreatment with picrotoxin and tamoxifen, but not formestane. We conclude that testosterone produced anxiolytic-like effects in female rats that were mediated by actions at the GABA(A) receptor, with participation of the estradiol receptor-beta, rather than estradiol aromatization.