Serum estradiol levels and ethanol-induced aggression

Pro-social and anxiolytic-like behavior following a single 24-h exposure to 17β-estradiol in adult male zebrafish

Estradiol (17β-estradiol, E₂) is a crucial estrogen hormone that regulates sexual, cognitive, social and affective behaviors in various species. However, complex central nervous system (CNS) effects of E₂, including its activity in males, remain poorly understood. The zebrafish (Danio rerio) is rapidly becoming a powerful novel model system in translational neuroscience research. Here, we evaluate the effects of a single 24-h exposure to 20 μg/L of E₂ on behavioral and endocrine (cortisol) responses in adult male zebrafish. Overall, E₂ exerted pro-social effect in the social preference test, reduced whole-body cortisol levels, elevated exploration in the novel tank test and increased the shoal size in the shoaling test, indicative of an anxiolytic-like profile of this hormone in male zebrafish. Supporting mounting human and rodent evidence on the role of E₂ in behavioral regulation, the observed pro-social and anxiolytic-like effects of E₂ in male zebrafish reinforce the use of this aquatic organism in studying steroid-mediated CNS mechanisms of complex affective and social behaviors.

Beer consumption negatively regulates hormonal reproductive status and reduces apoptosis in Leydig cells in peripubertal rats

Beer is one of the most popular alcoholic beverages consumed by young people. Ethanol intake is associated with harmful effects to the reproductive system. Bioactive compounds present in beer may diminish the toxics effect of ethanol. However, there is still little knowledge about the effect of beer consumption on hormonal regulation of male reproduction in organisms exposed to alcohol after the peripubertal age. Therefore, the aim of this study was to determine the influence of beer intake on plasma reproductive hormones, immunolocalization of cleaved caspase-3 (casp-3), and the level of the neuronal isoform of nitric oxide synthase (nNOS) in Leydig cells (LCs) in adolescent male Wistar rats. The animals, beginning at the age of 30 days, drank beer (10% ethanol; B2 group [2 weeks' exposure] and B4 group [4 weeks' exposure]), 10% ethanol solution (CE2 group [2 weeks' exposure] and CE4 group [4 weeks' exposure]), or water (C2 group [2 weeks' exposure] and C4 group [4 weeks' exposure]). Rats drinking beer for 4 weeks showed higher phenolic acid intake compared to rats drinking beer for 2 weeks. Rats exposed to beer for 4 weeks showed decreased plasma levels of follicle-stimulating hormone (FSH) and 17β-estradiol (E2) (3.173 ng/mL and 11.49 pg/mL, respectively), compared to the CE4 (5.293 ng/mL and 43.912 pg/mL, respectively) and the C4 groups (5.002 ng/mL and 41.121 pg mL, respectively). Expression of cleaved caspase-3 in LCs was lower in the B4 group rats, compared to the CE4 group rats (ID score: 1.676 vs. 2.190). No changes in nNOS expression were observed. Beer consumption revealed a similar negative effect on hormonal regulation of male reproductive function, but lower apoptosis in LCs may be beneficial for steroidogenic activity.

Direct and indirect protection of right ventricular function by estrogen in an experimental model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) results in right ventricular (RV) dysfunction and failure. Paradoxically, women are more frequently diagnosed with PAH but have better RV systolic function and survival rates than men. The mechanisms by which sex differences alter PAH outcomes remain unknown. Here, we sought to study the role of estrogen in RV functional remodeling in response to PAH. The SU5416-hypoxia (SuHx) mouse model of PAH was used. To study the role of estrogen, female mice were ovariectomized and then treated with estrogen or placebo. SuHx significantly increased RV afterload and resulted in RV hypertrophy. Estrogen treatment attenuated the increase in RV afterload compared with the untreated group (effective arterial elastance: 2.3 ± 0.1 mmHg/μl vs. 3.2 ± 0.3 mmHg/μl), and this was linked to preserved pulmonary arterial compliance (compliance: 0.013 ± 0.001 mm(2)/mmHg vs. 0.010 ± 0.001 mm(2)/mmHg; P < 0.05) and decreased distal muscularization. Despite lower RV afterload in the estrogen-treated SuHx group, RV contractility increased to a similar level as the placebo-treated SuHx group, suggesting an inotropic effect of estrogen on RV myocardium. Consequently, when compared with the placebo-treated SuHx group, estrogen improved RV ejection fraction and cardiac output (ejection fraction: 57 ± 2% vs. 44 ± 2% and cardiac output: 9.7 ± 0.4 ml/min vs. 7.6 ± 0.6 ml/min; P < 0.05). Our study demonstrates for the first time that estrogen protects RV function in the SuHx model of PAH in mice directly by stimulating RV contractility and indirectly by protecting against pulmonary vascular remodeling. These results underscore the therapeutic potential of estrogen in PAH.

Puberty, hormones, and sex differences in alcohol abuse and dependence

Sex differences in patterns of drinking and rates of alcohol abuse and dependence begin to emerge during the transition from late puberty to young adulthood. Increases in pubertal hormones, including gonadal and stress hormones, are a prominent developmental feature of adolescence and could contribute to the progression of sex differences in alcohol drinking patterns during puberty. This paper reviews experimental and correlational studies of gonadal and stress-related hormone changes and their effects on alcohol drinking and other associated actions of alcohol. Mechanisms are suggested by which reproductive hormones and stress-related hormones may modulate neural circuits within the brain reward system to produce sex differences in alcohol drinking patterns and vulnerability to alcohol abuse and dependence which become apparent during the late pubertal period.

The progesterone challenge: steroid hormone changes following a simulated territorial intrusion in female Peromyscus californicus

There is a growing body of evidence that the rapid but transient increase in male androgens, particularly testosterone (T), following a single social encounter such as a territorial intrusion occurs in a wide array of vertebrate taxa. Yet, this phenomenon, often called the Challenge Hypothesis, has rarely been investigated in females. Moreover, when studying male challenge effects, researchers have rarely investigated other hormones that can be important to the expression of aggression, such as progesterone (P4) and estradiol (E2). We conducted 10-min aggression trials using the resident-intruder paradigm in cycling female California mice, Peromyscus californicus, a species in which both sexes show territorial behavior. By comparing the hormone levels of test females to control females, we found a decrease in P(4) and the P4/T ratio, but no change in T, E2, corticosterone, E2/P4, or E2/T. Interestingly, these hormone changes were observed even when the resident was not aggressive toward the intruder, suggesting that the stimulus cueing the hormone changes was the mere presence of the intruder and not the amount of aggression displayed by the resident. Generally, T has a positive relationship with aggression, whereas P4 inhibits male and nonmaternal female aggression. Thus, decreasing the P4/T ratio following an encounter may serve to increase future aggression in females. These results suggest that females may use different hormonal mechanisms than do males to mediate aggression in a challenge situation.

Disruption of pubertal onset by exogenous testosterone and estrogen in two species of rodents

The administration of adult physiological levels of testosterone (T) and 17beta-estradiol (E(2)) to male Siberian hamsters was previously shown to delay the onset of puberty. To examine whether this is a response common to other rodents, we investigated whether exogenous steroids also alter the onset of puberty in Syrian hamsters and mice. Juvenile male Syrian hamsters and mice were implanted with Silastic capsules containing T, E(2), or cholesterol control. After 15 days, plasma, pituitaries, and testes were processed for histological analysis or measurements of gonadotropins and circulating steroid hormones. T and E(2) implants reduced testis mass and gonadotropin stores in both species and arrested spermatogenesis in Syrian hamsters. In contrast, spermatogenesis in mice was unaffected by T and only modestly affected by E(2). Although E(2) inhibited circulating follicle-stimulating hormone (FSH) in both species, T inhibited circulating FSH in mice only. Overall, our results demonstrate that the hypothalamic-pituitary-gonadal axis of each rodent species responds uniquely to T and E(2) during the pubertal transition. Despite the highly varied effects of T and E(2) in these two species, the ability of steroid hormones to disrupt the onset of puberty appears to be a feature common to many rodents.

Myocardial ischemia-reperfusion injury in estrogen receptor-alpha knockout and wild-type mice

We investigated the function of estrogen receptor-alpha in global myocardial ischemia and reperfusion injury in male estrogen receptor-alpha knockout (ERKO) and wild-type mice. Mouse hearts were subjected to 45 min of global ischemia followed by 180 min of reperfusion. The hearts were excised, cannulated, and maintained in a chilled (4 degrees C) cardioplegia solution until warm (37 degrees C) oxygenated Krebs-Henseleit bicarbonate buffer was perfused through the coronary arteries. ERKO hearts started beating later and had a higher incidence of ventricular fibrillation and/or tachycardia than control hearts. Coronary flow rate was significantly lower in ERKO hearts during the 90- and 120-min periods of reperfusion. Ca(2+) accumulation was significantly greater following 30, 90, 120, 150, and 180 min of reperfusion in ERKO hearts. Nitrite production was significantly less in ERKO hearts following 90, 120, and 150 min of reperfusion. Myocardial reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was significantly lower in experimental ERKO hearts. Marked interstitial edema and contraction bands were seen in hematoxylin-eosin-stained sections of ischemia-reperfused ERKO hearts but not in control tissues. Hematoxylin-basic fuchsin-picric acid-stained sections from experimental ERKO hearts had fewer viable myocytes compared with controls. Transmission electron microscopy revealed swollen and fragmented mitochondria with amorphous and granular bodies, loss of matrix, and rupture of cristae in experimental ERKO hearts. This is the first demonstration that estrogen receptor-alpha plays a cardioprotective role in ischemia-reperfusion injury in males.

The influence of gonadal steroids on pre-pro melanin-concentrating hormone mRNA in female rats

Melanin-concentrating hormone (MCH) may have a regulatory role in the control of luteinizing hormone (LH) release. We have investigated if gonadal steroids induce changes in the expression of pre-pro MCH (ppMCH) that are associated with changes in the pattern of LH release. Using quantitative in-situ hybridization histochemistry we have determined the effect of administration of either oestradiol benzoate (5 microg/rat) or oestradiol benzoate followed 44 or 48 h later by progesterone (0.5 mg/rat) to ovariectomized rats on the expression of ppMCH in the medial and lateral zona incerta and the lateral hypothalamus. The prevalence of ppMCH transcripts in the intact female rat at 12.00 and 19.00 h on proestrus and the first day of dioestrus was also examined. Oestrogen reduced the intensity of hybridization signal for ppMCH mRNA and this was associated with both a decrease in the number of cells in which the message was detected in the medial zona incerta and a negative feedback effect on LH release in ovariectomized rats. Progesterone administration to oestradiol benzoate-primed rats did not alter the reduced expression in the medial zona incerta in spite of its positive feedback effect on LH release. We suggest that progesterone may act only on post-translational events. Expression in the MCH cell bodies of the lateral zona incerta were not affected but there was a transient decrease 4 h after progesterone treatment in the oestradiol benzoate-primed rats in expression in the lateral hypothalamus. No changes in ppMCH mRNA were seen in intact animals on proestrus or the first day of dioestrus indicating that gonadal steroids are not important in the modulation of ppMCH gene expression during the oestrous cycle. In other steroid-dependent physiological situations, however, oestrogen may influence the expression of ppMCH in a subpopulation of cell bodies in the medial zona incerta.

Estrogen-regulated non-reproductive behaviors and breast cancer risk: animal models and human studies

The possible role of personality patterns and psychosocial factors in breast cancer has been studied extensively, through both human and animal experiments. The data are conflicting, and the conclusions controversial. This review will serve two purposes. First, we present evidence that behavioral patterns most commonly linked to breast cancer risk are at least partly regulated by estrogens. This section will suggest that some estrogen-regulated behaviors may be markers of increased breast cancer risk. Second, we will briefly review recent findings in animals connecting psychosocial factors to cancer. We also will address the plausible biological mechanisms. The literature suggests that estrogens, particularly when exposure occurs during the critical developmental periods, such as in utero, puberty, pregnancy, and menopause, influence affective behaviors and increase breast cancer risk. The affective behaviors include depression, aggression, and alcohol intake. Thus, psychosocial and personality factors do not necessarily have a direct impact on breast cancer risk; instead, estrogens have a dual effect on behavior and on the breast.