Diethylstilbestrol impaired oogenesis of yellow catfish juveniles through disrupting hypothalamic–pituitary–gonadal axis and germ cell development

Diethylstilbestrol (DES), a non‐steroidal estrogen, has been found to cause altered germ cell development and disordered ovarian development in fish females. However, the mechanisms that might be involved are poorly understood. In this study, female juveniles of yellow catfish (Pelteobagrus fulvidraco) (120 days post‐hatching) were exposed to two doses (10 and 100 ng l^?1) of DES for 28 days. After the endpoint of exposure, decreased ovary weight and gonadosomatic index, as well as various ovarian impairments were observed in response to DES. Besides, DES elevated the mRNA levels of vitellogenin 1 (vtg 1) and estrogen receptor 1 (esr 1) in liver and decreased 17β‐estradiol level in plasma. Correspondingly, suppressed mRNA levels of the key genes in the hypothalamic–pituitary–gonadal axis (such as cyp19a1b, gnrh‐II, fshβ and lhβ in brain and fshr, lhr and cyp19a1a in ovary) after DES exposure were also observed. The declined level of plasma 17β‐estradiol and altered gene expressions of genes in the hypothalamic–pituitary–gonadal axis were thus supposed to be closely related to the disrupted oogenesis in DES‐treated fish. Analyses further demonstrated that, higher concentration of DES elevated the expression ratio of bax/bcl‐2, indicating the enhanced apoptosis occurred in ovary. Moreover, DES upregulated the expressions of genes involved in proliferation (cyclin d1 and pcna), meiotic entry (cyp26a1 and scp3) and meiotic maintenance (dmc1), resulting in arrested oogenesis in catfish. The present study greatly extended our understanding on the mechanisms underlying of reproductive toxicity of DES on fish oogenesis.     

Determination of GnRH and its synthetic analogues' abuse in doping control: Small bioactive peptide UPLC–MS/MS method extension by addition of in vitro and in vivo metabolism data; evaluation of LH and steroid profile parameter fluctuations as suitable biomarkers

Gonadotropin‐releasing hormone (GnRH) and its small peptide synthetic analogues are included in Section S2 of the World Anti‐Doping Agency (WADA) Prohibited List as they stimulate pituitary luteinizing hormone (LH) and testicular testosterone (T) secretion. Both the following approaches can be applied for determination of abuse of these peptides: direct identification of intact compounds and their metabolites in athletes' biofluids and evaluation of LH and T concentrations as mediate markers of drug intake. To develop an effective concept for GnRH and its analogues determination in anti‐doping control, in vitro and in vivo studies were conducted. A new method was applied to the evaluation of the slow‐release profile of buserelin, goserelin, and leuprolide biodegradable microspheres after the intramuscular injection in male volunteers. Eight metabolites of 10 GnRH analogues were identified after incubation with human kidney microsomes, most of them were leuprolide degradation products. Obtained data were added into ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method for GnRH analogues determination. The detection time windows for administered peptides and their metabolites in urine samples were evaluated with 2 sample preparation techniques: dilute‐and‐shoot and solid‐phase extraction. To support the second hypothesis, the measurement of LH and the main parameters of the steroid profile were performed in urine samples. Just 1 compound among those investigated resulted in the LH concentration dropping to non‐physiological levels. Thus, for doping‐control purposes, monitoring of hormone levels fluctuations could be applied only together with longitudinal passport steroid profile data.     

Depression and alterations in hypothalamic–pituitary–adrenal and hypothalamic–pituitary–thyroid axis function in male abstinent methamphetamine abusers

The present study was to investigate depression and alterations in the hypothalamic–pituitary–adrenal (HPA) and hypothalamic–pituitary–thyroid (HPT) axis function in methamphetamine (METH) abusers after abstinence. Depression was assessed using the 13‐item Beck Depression Inventory (BDI‐13) scale; blood samples from in‐patients who were METH abusers and age‐matched and sex‐matched healthy controls were collected. The demographic characteristics and history of METH abuse also was assessed. We found that serum levels of adrenocorticotropic hormone (ACTH) and thyroxine were increased; and serum levels of cortisol, triiodothyronine, and thyroid‐stimulating hormone were decreased; and the BDI score was higher in METH abusers compared with control. In addition, there was no correlation between the BDI‐13 score and any of hormones of HPA and HPT axis was found. Particularly, we found abnormally higher ACTH level and mismatched with lower cortisol level in abstinent METH abusers. These results indicate that METH abusers and that their HPA and HPT functions are all altered after abstinence. Chronically using METH may destroy the regulatory function of the HPA axis, especially the feedback regulation of cortisol to ACTH. Copyright © 2013 John Wiley & Sons, Ltd.     

Relation among HPA and HPG neuroendocrine systems,transmissible risk and neighborhood quality on development of substance use disorder: Results of a 10-year prospective study

BackgroundResearch has shown involvement of hormones of the hypothalamic pituitary adrenal (HPA) axis and hypothalamic pituitary gonadal (HPG) axis in the regulation of behaviors that contribute to SUD risk and its intergenerational transmission. Neighborhood environment has also been shown to relate to hormones of these two neuroendocrine systems and behaviors associated with SUD liability. Accordingly, it was hypothesized that (1) parental SUD severity and neighborhood quality correlate with activity of the HPG axis (testosterone level) and HPA axis (cortisol stability), and (2) transmissible risk during childhood mediates these hormone variables on development of SUD measured in adulthood.MethodsTransmissible risk for SUD measured by the transmissible liability index (TLI; Vanyukov et al., 2009) along with saliva cortisol and plasma testosterone were prospectively measured in boys at ages 10–12 and 16. Neighborhood quality was measured using a composite score encompassing indicators of residential instability and economic disadvantage. SUD was assessed at age 22.ResultsNeither hormone variable cross-sectionally correlated with transmissible risk measured at ages 10–12 and 16. However, the TLI at age 10–12 predicted testosterone level and cortisol stability at age 16. Moreover, testosterone level, correlated with cortisol stability at age 16, predicted SUD at age 22.ConclusionHPA and HPG axes activity do not underlie variation in TLI, however, high transmissible risk in childhood predicts neuroendocrine system activity presaging development of SUD.     

Therapeutic potential of GnRH antagonists in the treatment of precocious puberty

Pituitary-gonadal axis activation depends upon pulsatile hypothalamic gonadotropin-releasing hormone (GnRH) secretion. This phenomenon has led to clinical use of GnRH agonists in the treatment of central precocious puberty. GnRH analogues contain substitutions of the native decapeptide. Depending upon the substitutions, the analogues have GnRH agonistic or antagonistic properties. The pharmacokinetics of GnRH agonists, the established treatment of precocious puberty, includes an initial 'flare-up' of the pituitary-gonadal axis, followed by a reduced luteinising hormone secretion by desensitisation of pituitary GnRH receptors. Antagonistic GnRH analogues act by competitive binding to the pituitary GnRH receptors, thereby preventing the action of endogenous GnRH - theoretically offering a more direct and dose-dependent treatment alternative. The antagonist available today in Germany is a concomitant in assisted reproduction with only 1 - 3 days duration. However, long-acting depot preparations of other GnRH antagonists are in primate-testing phase. Our animal tests indicate strong potential for the development and testing of long-acting depot preparations of GnRH antagonists in treating precocious puberty.     

Therapeutic potential of GnRH antagonists in the treatment of precocious puberty

Pituitary-gonadal axis activation depends upon pulsatile hypothalamic gonadotropin-releasing hormone (GnRH) secretion. This phenomenon has led to clinical use of GnRH agonists in the treatment of central precocious puberty. GnRH analogues contain substitutions of the native decapeptide. Depending upon the substitutions, the analogues have GnRH agonistic or antagonistic properties. The pharmacokinetics of GnRH agonists, the established treatment of precocious puberty, includes an initial ‘flare-up’ of the pituitary-gonadal axis, followed by a reduced luteinising hormone secretion by desensitisation of pituitary GnRH receptors. Antagonistic GnRH analogues act by competitive binding to the pituitary GnRH receptors, thereby preventing the action of endogenous GnRH – theoretically offering a more direct and dose-dependent treatment alternative. The antagonist available today in Germany is a concomitant in assisted reproduction with only 1 – 3 days duration. However, long-acting depot preparations of other GnRH antagonists are in primate-testing phase. Our animal tests indicate strong potential for the development and testing of long-acting depot preparations of GnRH antagonists in treating precocious puberty.     

Kisspeptin调节肽参与多囊卵巢综合征的研究进展

多囊卵巢综合征（PCOS）是常见的内分泌及代谢性疾病,其发病机制尚不清楚,下丘脑-垂体-卵巢轴（HPO轴）功能紊乱是PCOS发生的主要原因之一。Kisspeptin调节肽是下丘脑中的一种调节肽,可以和下丘脑内GPR54受体结合,促进下丘脑促性腺激素释放激素（GnRH）及促黄体生成素（LH）的分泌,造成HPO轴功能紊乱;Kisspeptin调节肽不仅存在于下丘脑中枢调控HPO轴,还可以在卵巢局部发挥作用,影响卵巢微环境,阻碍卵泡的成熟,调控PCOS的发生和发展。PCOS病人不仅存在生殖内分泌的异常,大多还存在糖脂代谢紊乱,Kisspeptin调节肽可能通过生殖内分泌及能量代谢的双重调节作用参与PCOS的发生。该研究将对Kisspeptin调节肽影响PCOS病人生殖内分泌、能量代谢及其临床应用进行综述,为进一步了解Kisspeptin调节肽和PCOS的关系提供参考。     

Mycotoxin zearalenone induced gonadal impairment and altered gene expression in the hypothalamic–pituitary–gonadal axis of adult female zebrafish (Danio rerio)

In the present study, we aimed to assess the adverse effects of zearalenone (ZEA) at environmentally relevant concentrations (0.5, 1, 5 and 10 μg l^?1) on hypothalamic–pituitary–gonadal axis associated reproductive function using zebrafish model. ZEA was exposed to female zebrafish for 21 days to assess growth indices such as condition factor, hepatosomatic index, gonadosomatic index and caspase 3 activity. Further, expression of estrogen receptor (ER) α and CYP19a1b genes in the brain, ERα and vitellogenin (Vtg) genes in the liver and follicle‐stimulating hormone receptor, luteinizing hormone receptor, ERα, steroidogenic acute regulatory protein, 3β‐hydroxysteroid dehydrogenase (HSD), 17‐βHSD and CYP19a1 genes in the ovary were also investigated. Our results showed that there were no significant changes in the condition factor and hepatosomatic index, whereas a significant (P < .05) reduction in the gonadosomatic index, increase in caspase 3 activities and Vtg expression was observed at higher concentration. However, no significant changes were observed at lower treatment levels. Further, we also observed significant (P < .05) upregulation in ERα, Vtg, luteinizing hormone receptor, steroidogenic acute regulatory protein, 3β‐HSD, 17β‐HSD, CYP19a1 and CYP19a1b genes in treatment groups with higher levels of ZEA. Moreover, in histopathological examination, we observed oocyte atresia and oocyte membrane detachment in ovaries at the highest concentration. In conclusion, the present study revealed the negative impact of ZEA on zebrafish reproductive system by involvement of the hypothalamic–pituitary–gonadal axis‐associated reproductive function.     

Alarin stimulates food intake and gonadotrophin release in male rats

BACKGROUND AND PURPOSE

Alarin is a recently discovered member of the galanin peptide family encoded by a splice variant of galanin-like peptide (GALP) mRNA. Galanin and GALP regulate energy homeostasis and reproduction. We therefore investigated the effects of alarin on food intake and gonadotrophin release.

EXPERIMENTAL APPROACH

Alarin was administered into the third cerebral ventricle (i.c.v.) of rats, and food intake or circulating hormone levels were measured. The effect of alarin on the hypothalamo–pituitary–gonadal axis was investigated in vitro using hypothalamic and anterior pituitary explants, and immortalized cell lines. Receptor binding assays were used to determine whether alarin binds to galanin receptors.

KEY RESULTS

The i.c.v. administration of alarin (30 nmol) to ad libitum fed male rats significantly increased acute food intake to 500%, and plasma luteinizing hormone (LH) levels to 170% of responses to saline. In vitro, 100 nM alarin stimulated neuropeptide Y (NPY) and gonadotrophin-releasing hormone (GnRH) release from hypothalamic explants from male rats, and 1000 nM alarin increased GnRH release from GT1-7 cells. In vivo, pretreatment with the GnRH receptor antagonist cetrorelix prevented the increase in plasma LH levels observed following i.c.v. alarin administration. Receptor binding studies confirmed alarin did not bind to any known galanin receptor, or compete with radiolabelled galanin for hypothalamic binding sites.

CONCLUSIONS AND IMPLICATIONS

These results suggest alarin is a novel orexigenic peptide, and that it increases circulating LH levels via hypothalamic GnRH. Further work is required to identify the receptor(s) mediating the biological effects of alarin.     

应激与生殖内分泌功能障碍

躯体和心理应激均能在HPG轴多水平抑制或损害生殖内分泌功能尤其是女性生殖内分泌功能 ,从而导致人类亚健康状态、临床生殖内分泌系统疾病 ,其发生机制与应激引起的下丘脑CRF和肾上腺GCS过度释放及其它神经内分泌改变密切相关 ,而生殖内分泌激素合成酶活性的应激性降低则为性激素降低和生殖内分泌系统功能紊乱的直接原因     

Progesterone affects sex differentiation and alters transcriptional of genes along circadian rhythm signaling and hypothalamic‐pituitary‐gonadal axes in juvenile Yellow River Carp (Cyprinus carpio var.)

Progesterone (P4) is a biologically active steroid hormone that is involved in the regulation of oocyte growth and maturation, as well as development of the endometrium and implantation in the uterus of humans. It can also stimulate oocyte maturation in female fish, as well as spermatogenesis and sperm motility in male fish. Thus, P4 has been extensively used in human and animal husbandry as a typical progestin. However, P4 remaining in the water environment will pose a potential hazard to aquatic organisms. For example, it can interfere with sex differentiation and reproduction in aquatic vertebrates such as fish. Therefore, we investigated the effects of prolonged progesterone exposure on the expression of genes related to circadian rhythm signaling and the hypothalamic‐pituitary‐gonadal (HPG) axes in Yellow River Carp, which may have a potential impact on their sex differentiation. Our results suggested that P4 exposure altered the expression of genes related to circadian rhythm signaling, which can lead to disorders in the endocrine system and regulate the HPG axes‐related activities. Furthermore, the expression of genes related to the HPG axes was also altered, which might affect gonadal development and the reproductive systems of Yellow River Carp. In addition, these changes may provide a plausible mechanism for the observed shifts in their sex ratio toward females.     

Alcohol abuse-duration dependent decrease in plasma testosterone and antioxidants in males

Ethanol is a testicular toxin and it causes fertility abnormalities with low sperm count and impaired sperm motility in men. The present study was designed to investigate plasma testosterone level and hypothalamic pituitary gonadal (HPG) axis function in alcoholic men and also effect of ethanol on systemic oxidative stress. Forty six male alcohol abusers in the age group 20-40 years were selected. Fifty five, males in the same age group served as control. Alcohol abusers had significantly low plasma testosterone with low luteinizing hormone and follicle stimulating hormone. In addition they had significantly high thiobarbituric acid reactive substances (TBARS), superoxide dismutase and glutathione S-transferase, and low glutathione, ascorbic acid, catalase, glutathione reductase and glutathione peroxidase. Moreover, serum testosterone level in alcoholics negatively correlated with duration of alcohol abuse, and TBARS. Duration dependent decreased serum testosterone level in alcohol abusers might be due to 1) increased oxidative stress which can damage Leydig and supporting Sertoli cells and 2) impaired HPG axis.     

GnRH analogues containing conformationally restricted amino acids in positions 3 and 6: differential impact on pituitary binding affinity and direct antiproliferative effect on breast cancer cells†

Abstract: Analogues of GnRH have been widely used in oncology and gynaecology to induce reversible chemical castration. In addition to the classic hypophysiotropic action of GnRH, it has been shown that many malignant cells, such as breast cancer cells, secrete GnRH and express the GnRH receptor/s. In order to study the effect of modifications in position 3 and 6 of GnRH on both pituitary binding affinity and breast cancer cell proliferation, we synthesized eight new GnRH analogues. All GnRH analogues lacked the carboxy–terminal Gly¹⁰–amide of GnRH and an ethylamide residue was added to Pro⁹. Gly⁶ was substituted by α,α‐dialkyl amino acids (Aib: α‐aminoisobutyric acid, Deg: diethylglycine) and Trp³ by D–Trp, D‐ and L‐1,2,3,4,‐tetrahydro‐isoquinoline‐3‐carboxylic acid (Tic). During competition binding experiments in mouse anterior pituitary αT3‐1 cells, [Aib⁶,desGly¹⁰]GnRH‐NHEt bound to the GnRH receptor with IC₅₀ values comparable to those of parent hormone in contrast to the analogues substituted at position 3 . However, [L‐Tic³,Deg⁶,desGly¹⁰]GnRH‐NHEt had high pituitary binding affinity. With the exception of GnRH and [Aib⁶,desGly¹⁰]GnRH‐NHEt, all GnRH analogues significantly inhibited the proliferation of human breast cancer cells (MCF‐7); higher inhibitory effect was observed for analogues modified at position 3 . Results show differential impact of the modifications on the binding affinity to the GnRH receptor in mouse pituitary cells and on the inhibition of human breast cancer cell proliferation and provide insight into structure‐activity relationship of GnRH in different biological systems.     

Short-term neonatal/prepubertal exposure of dibutyl phthalate (DBP) advanced pubertal timing and affected hypothalamic kisspeptin/GPR54 expression differently in female rats

Dibutyl phthalate (DBP) had been widely used and its exposure in children has been thought to be one of the reasons causing a trend of advanced pubertal timing in girls. Puberty starts from hypothalamic gonadotropin-releasing hormone release which is controlled by many factors including neurotransmitter kisspeptin and its receptor GPR54. These neural organization or reorganization happens in hypothalamus during neonatal or prepubertal period which may be two target windows of DBP exposure. The present study was designed to determine: (1) the difference between the effects of neonatal and prepubertal DBP exposure on female pubertal timing; (2) whether kisspeptin/GPR54 expression in hypothalamus would respond to neonatal and prepubertal DBP exposure differently. Female Sprague-Dawley rats were exposed by subcutaneous injection of 0.5, 5 and 50 mg/kg DBP during Postnatal day (P)1–5 (neonatal) or P26–30 (prepubertal). Physiological data demonstrated that both neonatal and prepubertal DBP exposure could advance pubertal timing significantly accompanied by irregular estrous cycles but only a little gonadal impairment. Exposure-period-related difference was found significant with prepubertal exposure groups having longer estrous cycle duration, heavier at vaginal opening and having higher serum estradiol level compared with neonatal exposure groups. Molecular data showed an up-regulated trend in kisspeptin mRNA and immunoreactivity levels of hypothalamic area arcuate but a down-regulation in GPR54 mRNA expression after P1–5 DBP treatment. In P26–30 groups, kisspeptin mRNA and immunoreactivity levels tended to be lower after DBP treatment. These results demonstrated small dose of DBP could induce earlier pubertal timing in females and both neonatal and prepubertal periods were critical windows for DBP exposure.     

大补阴丸对真性性早熟模型大鼠的治疗作用

目的探讨大补阴丸对真性性早熟大鼠的治疗作用,评价大补阴丸对真性性早熟的疗效并探讨可能的作用机制。方法 5日龄SD雌性大鼠一次性sc给予达那唑30μg.g-1建立性早熟模型。15日龄时开始ig给予大补阴丸0.81,1.62和3.24 g·kg-1,每天1次,至模型组大鼠阴门开启数超过50%。21日龄起,密切观察各组大鼠阴门开启情况,并记录开启时的日龄。对阴门已开启的大鼠,于每日早晨进行阴道脱落细胞涂片,显微镜下观察性周期的变化。当模型组阴门开启大鼠数超过该组的50%时(33日龄),所有大鼠股动脉放血处死,取子宫和卵巢计算子宫和卵巢系数,并常规制作子宫和卵巢组织切片测定子宫壁厚度和卵巢黄体生成数;半定量逆转录(RT)-PCR法测定下丘脑促性腺激素释放激素(GnRH)、G蛋白偶联受体54(GPR54)和Kiss-1 mRNA的表达水平。结果大补阴丸3.24 g·kg-1组子宫系数为115±12,较模型组154±14显著降低(P<0.05);大补阴丸3.24 g·kg-1组子宫壁厚度为(166±27)μm,较模型组(477±71)μm显著降低(P<0.05),并使卵巢黄体生成个数显著减少;大补阴丸能明显降低下丘脑GnRH,GPR54和Kiss-1mRNA的表达水平,卵巢系数则无明显变化。结论大补阴丸可能通过抑制下丘脑Kiss-1和GPR54基因表达,抑制下丘脑GnRH的合成和释放,从而抑制下丘脑-垂体-性腺轴的启动,发挥治疗真性性早熟的作用。     

CAGn repeat of the androgen receptor is linked to proopiomelanocortin promoter methylation—relevance for craving of male alcohol-dependent patients?

Rationale

Previous findings of the Franconian Alcoholism Research Studies showed that both the CAGn of the androgen receptor (AR) and the promoter methylation of the hypothalamic peptide proopiomelanocortin (POMC) were associated with craving of male alcohol-dependent patients.

Objectives

Based on the strong interactions between the hypothalamic–pituitary–gonadal (HPG) and the hypothalamic–pituitary–adrenal axis (HPA), this study investigated the relationships between the CAGn repeat of the AR, POMC promoter methylation and craving of male alcohol-dependent patients.

Methods

This analysis covers 84 male patients with a diagnosis of alcohol dependence (DSM-IV). We sequenced the POMC gene promoter using bisulfite modified DNA to display the methylation status. Furthermore, we sequenced the CAGn repeat within exon 1 of the AR gene. Craving was quantified by the Obsessive Compulsive Drinking Scale.

Results

We found an inverse correlation between the number of CAGn repeats of the AR and the POMC methylation status in this study. Altogether, the POMC promoter methylation accounted for 33 % of the relationship between CAGn AR polymorphism and craving.

Conclusions

This work shows that the AR and the POMC gene might functionally interact with each other and subsequently mediate craving in alcohol-dependent patients. The paper discusses different mechanisms which might underlie our findings involving sex hormones' and sex determining region of Y-gene's regulatory function on DNA-methyltransferase activity. In conclusion, the results give insight in the interaction between HPG and HPA axis. This study is a further step on the way to a better understanding of genetic and non-genetic factors underlying craving for alcohol.     

Kisspeptin-54 at high doses acutely induces testicular degeneration in adult male rats via central mechanisms

Background and purpose:

The kisspeptins are critical regulators of reproduction and a therapeutic target for reproductive disease. Intracerebroventricular (i.c.v.) or peripheral injection of kisspeptin potently stimulates the hypothalamic-pituitary gonadal (HPG) axis via gonadotrophin-releasing hormone (GnRH). However, little is known regarding the effects of kisspeptin administration on testicular function. We investigated the mechanism(s) of kisspeptin-induced testicular degeneration in the rat.

Experimental approach:

Kisspeptin-54 (50 nmol·day⁻¹) was continuously administered subcutaneously (6 h to 3 days) to male Wistar rats and reproductive hormones and testicular histology analysed. We also investigated the effects of a single subcutaneous injection of 0.5, 5 or 50 nmol kisspeptin-54. In order to determine whether the testicular degeneration observed is peripherally or centrally mediated, we investigated effects of i.c.v. injections of 5 nmol kisspeptin-54 and pre-administered a GnRH-receptor antagonist (cetrorelix) to rats peripherally treated with kisspeptin-54.

Key results:

Continuous subcutaneous administration of kisspeptin-54 caused testicular degeneration after only 12 h, when gonadotrophins were still markedly raised, suggesting that the degeneration is independent of the desensitization of the HPG axis to kisspeptin-54. Furthermore, a single subcutaneous injection of kisspeptin-54 caused dose-dependent testicular degeneration. Continuous kisspeptin-54 administration is thus not required to cause testicular degeneration. Pretreatment with cetrorelix blocked kisspeptin-induced testicular degeneration, and a single i.c.v. injection of kisspeptin-54 caused testicular degeneration, suggesting it is GnRH-mediated.

Conclusions and implications:

Kisspeptin-induced testicular degeneration appears to be centrally mediated, and result from acute hyper-stimulation of the HPG axis. Doses must be carefully considered if kisspeptin is to be used therapeutically.     

Developmental fluoxetine exposure facilitates sexual behavior in female offspring

Rationale

A growing number of infants are being exposed to selective serotonin reuptake inhibitor (SSRI) medications during the perinatal period. SSRIs target the serotoninergic system and are a popular treatment for maternal mood disorders. Serotonin itself plays a key role in the sexual differentiation through its role in the development of the hypothalamic–pituitary–gonadal axis, and previous research has shown that developmental SSRI exposure has an effect on sexual behavior in male offspring.

Objectives

Our aim was to determine the role of developmental exposure to a popular SSRI medication, fluoxetine, on sexual differentiation of the brain and behavior in female offspring using a rodent model of maternal adversity.

Methods

Stressed and non-stressed Sprague–Dawley rat dams were chronically treated with either fluoxetine (5 mg/kg/day) or vehicle beginning on postnatal day 1. Four groups of female offspring were used: (1) control?+?vehicle, (2) control?+?fluoxetine, (3) prenatal stress?+?vehicle, and (4) prenatal stress?+?fluoxetine.

Results

Primary results show that in adult female offspring, developmental fluoxetine exposure facilitates proceptive and receptive behaviors with a significant increase in the number of proceptive behaviors, a significant increase in the lordosis quotient, and a significant decrease in the rejection quotient.

Conclusions

This research contributes in the understanding of the long-term impact developmental fluoxetine exposure on the hypothalamus–pituitary–gonadal (HPG) system in adult female offspring.     

Effects of low subchronic doses of methoxychlor on the rat hypothalamic-pituitary reproductive axis

The pesticide methoxychlor (MXC) is known to possess a weak estrogenic action and has been found to have a number of toxic effects on the rodent reproductive system, primarily at the gonadal level. The purpose of this study was to explore the influence of MXC on the pituitary and hypothalamic components of the male reproductive system at dose levels that were without detectable testicular effects. At 21 days, male Long-Evans rats were gavaged daily with 25 or 50 mg/kg MXC in corn oil. Controls received vehicle only. After 8 weeks of dosing, no significant changes were seen in serum LH, FSH, or prolactin, nor in the pituitary concentrations of LH or FSH. Pituitary prolactin was elevated for both doses, and pituitary fragments perifused in vitro released more prolactin than did controls. The concentration of gonadotropin-releasing hormone (GnRH) was higher in the mediobasal hypothalamus, but only for the 50-mg/kg group. At this dose, there was a corresponding increase in the KCl-stimulated release of GnRH. The data suggest that previously reported reproductive effects of MXC may be mediated, at least in part, through an elevation in prolactin concentration and release, which in turn is able to influence hypothalamic levels of GnRH. This prolactinemic effect may well represent an early component of the adverse action of MXC on the reproductive system.