Hypothalamic Luteinizing Hormone-releasing Hormone Research Articles

TRATAMENTO MEDICAMENTOSO DOS TRANSTORNOS PARAFÍLICOS

O objetivo deste artigo foi apresentar as medicações utilizadas para o tratamento de Transtornos Parafílicos (TP), seus mecanismos de ação, efeitos colaterais e a importância das comorbidades presentes para a escolha da melhor droga para cada caso. Foi realizada revisão de literatura no Pubmed e Medline. Muitas medicações podem ser úteis: antidepressivos que agem no receptor serotoninérgico5HT2a, especialmente em casos de depressão e doenças ansiosas;antipsicóticos, que são antidopaminérgicos, em psicoses; estabilizadores de humor em transtorno bipolar e impulsividade; naltrexona no alcoolismo; antiandrógenos de ação periférica ou central como os agonistas parciais do hormônio liberador de gonadotrofina hipotalâmico (agonistasLHRH), em casos mais severos. O melhor tratamento para cada indivíduo depende dos diagnósticos (sexual, psiquiátrico e médico geral). Tratar um indivíduo com doença de Wilson, psicose orgânica e transtorno exibicionista é diferente de trat ar um indivíduo com o mesmo TP, hipotireoidismo e depressão. É também importante tentar preservar a função sexual da maneira mais saudável possível. Por outro lado, é fundamental proteger a sociedade dos agressores sexuais. Questões éticas como a possibilidade de toxicidade das medicações devem ser amplamente discutidas e documentadas. Destaca-se o fato de que o uso de antiandrógenos para castração química não é liberado no Brasil.

Expression of hypothalamic neurohormones and their receptors in the human eye.

Extrapituitary roles for hypothalamic neurohormones have recently become apparent and clinically relevant, based on the use of synthetic peptide analogs for the treatment of multiple conditions including cancers, pulmonary edema and myocardial infarction. In the eye, it has been suggested that some of these hormones and their receptors may be present in the ciliary body, iris, trabecular meshwork and retina, but their physiological role has yet to be elucidated. Our study intends to comprehensively demonstrate the expression of some hypothalamic neuroendocrine hormones and their receptors within different retinal and extraretinal structures of the human eye. Immunofluorescence, Western blot analysis, and RT-PCR were used to evaluate the qualitative and quantitative expression of Luteinizing Hormone Releasing Hormone (LHRH), Growth Hormone Releasing Hormone (GHRH), Thyrotropin Releasing Hormone (TRH), Gastrin Releasing Peptide (GRP) and Somatostatin as well as their respective receptors (LHRH-R, GHRH-R, TRH-R, GRP-R, SST-R1) in cadaveric human eye tissue and in paraffinized human eye tissue sections. The hypothalamic hormones LHRH, GHRH, TRH, GRP and Somatostatin and their respective receptors (LHRH-R, GHRH-R, TRH-R, GRPR/BB2 and SST-R1), were expressed in the conjunctiva, cornea, trabecular meshwork, ciliary body, lens, retina, and optic nerve.

Discovery of LHRH and development of LHRH analogs for prostate cancer treatment.

The discovery, isolation, elucidation of structure, synthesis, and initial testing of the neuropeptide hypothalamic luteinizing hormone-releasing hormone (LHRH), which regulates reproduction, is briefly described. The design, synthesis, and experimental and clinical testing of agonistic analogs of LHRH is extensively reviewed focusing on the development of new methods for the treatment of prostate cancer. Subsequent development of antagonistic analogs of LHRH is then faithfully recounted with special emphasis on therapy of prostate cancer and BPH. The concepts of targeted therapy to peptide receptors on tumors are re-examined and the development of the cytotoxic analogs of LHRH and their status is reviewed. The endeavor to develop better therapies for prostate cancer, based on LHRH analogs, guided much of our work.

Manganese-Stimulated Kisspeptin Is Mediated by the IGF-1/Akt/Mammalian Target of Rapamycin Pathway in the Prepubertal Female Rat.

Low-dose administration of manganese chloride (MnCl2) causes release of hypothalamic LH-releasing hormone (LHRH) and advances puberty in rat. Recently, this element was shown to up-regulate mammalian target of rapamycin (mTOR), kisspeptin gene (KiSS-1), and LHRH gene expressions in the brain preoptic area (POA)/anteroventral periventricular (AVPV) nucleus. Because these genes are critical for puberty, this study was conducted to identify the upstream mechanism by which Mn activates the mTOR/KiSS-1 pathway. On day 12, immature female rats began receiving a daily supplemental dose of 10 mg/kg of MnCl2 or saline by gavage, and POA/AVPV tissues were collected on day 29 for specific protein assessments. Another experiment assessed in vitro IGF-1 release in response to Mn and assessed signal transduction pathways in the POA/AVPV region after Mn delivery into the third ventricle. Chronic Mn exposure increased (P < .05) basal expressions of mTOR and kisspeptin proteins. Mn increased protein kinase B (Akt) and Ras homolog enriched in brain, both capable of activating mTOR. Central Mn delivery increased expressions of phosphorylated IGF-1 receptor (IGF-1R) (P < .05) and Akt (P < .01) in the POA/AVPV region. The previous central delivery of JB1, an IGF-1R antagonist, blocked Mn-induced expressions of both phosphorylated IGF-1R and Akt. Downstream to Akt, centrally administered Mn increased tuberous sclerosis complex 2 (P < .05), Ras homolog enriched in brain (P < .01), mTOR (P < .05), and kisspeptin (P < .05). Finally, we observed that the early puberty induced by Mn was blocked by the administration of an mTOR inhibitor. These results suggest that Mn acts, at least in part, through the IGF-1/Akt/mTOR pathway to influence prepubertal kisspeptin and LHRH.

Manganese protects against the effects of alcohol on hypothalamic puberty-related hormones

AimsSince manganese (Mn) is capable of stimulating the hypothalamic-pituitary unit and advancing female puberty, we assessed the possibility that this element might overcome some of the detrimental effects of prepubertal alcohol (ALC) exposure on the hypothalamic control of pituitary function. Main methodsRats received either saline or Mn (10mg/kg) daily by gastric gavage from day 12 to day 31. After weaning, all rats were provided Lab Chow diet ad libitum until day 27 when they began receiving either the Bio Serv control or ALC diet regime. On day 31, the medial basal hypothalamus (MBH) was collected to assess luteinizing hormone-releasing hormone (LHRH) and cyclooxygenase 2 (COX2) protein levels. Release of prostaglandin-E2 (PGE2), LHRH and serum luteinizing hormone (LH) were also assessed. Other animals were not terminated on day 31, but remained in study to assess timing of puberty. Key findingsShort-term ALC exposure caused elevated hypothalamic LHRH content, suggesting an inhibition in peptide release, resulting in a decrease in LH. Both actions of ALC were reversed by Mn supplementation. COX2 synthesis, as well as PGE2 and LHRH release were suppressed by ALC exposure, but Mn supplementation caused an increase in COX2 synthesis and subsequent PGE2 and LHRH release in the presence of ALC. Mn supplementation also ameliorated the action of ALC to delay puberty. SignificanceThese results suggest that low level Mn supplementation acts to protect the hypothalamus from some of the detrimental effects of ALC on puberty-related hormones.

Differential Effects of Alcohol on Excitatory and Inhibitory Puberty-Related Peptides in the Basal Hypothalamus of the Female Rat.

An increase in development of excitatory inputs along with a decline in inhibitory inputs ultimately govern the timely increased secretion of hypothalamic luteinizing hormone-releasing hormone (LHRH) at the time of puberty. As chronic alcohol (ALC) exposure acts at the hypothalamic level to suppress LHRH secretion and delay puberty, we assessed its ability to differentially affect the expression of key puberty-related proteins. ALC was administered to female rats from days 27 to 33, at which time animals were killed and tissues collected for protein expression. In the medial basal hypothalamus (MBH), we assessed kisspeptin (Kp) 10, an excitatory peptide critical for prepubertal LHRH secretion, and Lin28b, a peptide with an inhibitory influence on puberty. As a direct mechanism of action of Lin28b was not known, we determined whether its central administration could induce dynorphin (DYN), a peptide that is inhibitory on LHRH secretion. Also, ALC's effect on DYN protein expression was assessed, as well as its effect on DYN release in vitro. ALC markedly suppressed (p < 0.01) the expression of the excitatory Kp protein, while at the same time increased (p < 0.001) the expression of inhibitory Lin28b protein. Subsequently, we showed for the first time that the central administration of Lin28b stimulated (p < 0.01) the synthesis of DYN. Finally, ALC also induced (p < 0.01) the protein expression and stimulated (p < 0.01) the in vitro release of DYN from the MBH. These results indicate that ALC can simultaneously and differentially alter both excitatory and inhibitory influences governing pubertal development, show for the first time a mechanism of action by which Lin28b exerts its prepubertal inhibitory tone, and further demonstrate the negative influences of ALC on the pubertal process.

Alcohol alters hypothalamic glial-neuronal communications involved in the neuroendocrine control of puberty: In vivo and in vitro assessments

The onset of puberty is the result of the increased secretion of hypothalamic luteinizing hormone-releasing hormone (LHRH). The pubertal process can be altered by substances that can affect the prepubertal secretion of this peptide. Alcohol is one such substance known to diminish LHRH secretion and delay the initiation of puberty. The increased secretion of LHRH that normally occurs at the time of puberty is due to a decrease of inhibitory tone that prevails prior to the onset of puberty, as well as an enhanced development of excitatory inputs to the LHRH secretory system. Additionally, it has become increasingly clear that glial-neuronal communications are important for pubertal development because they play an integral role in facilitating the pubertal rise in LHRH secretion. Thus, in recent years attempts have been made to identify specific glial-derived components that contribute to the development of coordinated communication networks between glia and LHRH cell bodies, as well as their nerve terminals. Transforming growth factor-α and transforming growth factor-β1 are two such glial substances that have received attention in this regard. This review summarizes the use of multiple neuroendocrine research techniques employed to assess these glial-neuronal communication pathways involved in regulating prepubertal LHRH secretion and the effects that alcohol can have on their respective functions.

Transplantation of bovine adrenocortical cells encapsulated in alginate

Current treatment options for adrenal insufficiency are limited to corticosteroid replacement therapies. However, hormone therapy does not replicate circadian rhythms and has unpleasant side effects especially due to the failure to restore normal function of the hypothalamic-pituitary-adrenal (HPA) axis. Adrenal cell transplantation and the restoration of HPA axis function would be a feasible and useful therapeutic strategy for patients with adrenal insufficiency. We created a bioartificial adrenal with 3D cell culture conditions by encapsulation of bovine adrenocortical cells (BACs) in alginate (enBACs). We found that, compared with BACs in monolayer culture, encapsulation in alginate significantly increased the life span of BACs. Encapsulation also improved significantly both the capacity of adrenal cells for stable, long-term basal hormone release as well as the response to pituitary adrenocorticotropic hormone (ACTH) and hypothalamic luteinizing hormone-releasing hormone (LHRH) agonist, [D-Trp6]LHRH. The enBACs were transplanted into adrenalectomized, immunodeficient, and immunocompetent rats. Animals received enBACs intraperitoneally, under the kidney capsule (free cells or cells encapsulated in alginate slabs) or s.c. enclosed in oxygenating and immunoisolating βAir devices. Graft function was confirmed by the presence of cortisol in the plasma of rats. Both types of grafted encapsulated cells, explanted after 21-25 d, preserved their morphology and functional response to ACTH stimulation. In conclusion, transplantation of a bioartificial adrenal with xenogeneic cells may be a treatment option for patients with adrenocortical insufficiency and other stress-related disorders. Furthermore, this model provides a microenvironment that ensures 3D cell-cell interactions as a unique tool to investigate new insights into cell biology, differentiation, tissue organization, and homeostasis.

Alcohol alters insulin-like growth factor-1-induced transforming growth factor β1 synthesis in the medial basal hypothalamus of the prepubertal female rat.

Insulin-like growth factor-1 (IGF-1) and transforming growth factor β1 (TGFβ1) are produced in hypothalamic astrocytes and facilitate luteinizing hormone-releasing hormone (LHRH) secretion. IGF-1 stimulates release by acting directly on the LHRH nerve terminals and both peptides act indirectly through specific plastic changes on glial/tanycyte processes that further support LHRH secretion. Because the relationship between these growth factors in the hypothalamus is not known, we assessed the ability of IGF-1 to induce TGFβ1 synthesis and release and the actions of alcohol (ALC) on this mechanism prior to the onset of puberty. Hypothalamic astrocytes were exposed to medium only, medium plus IGF-1 (200ng/ml), or medium plus IGF-1 with 50mM ALC. After 18hours, media were collected and assayed for TGFβ1. For the in vivo experiment, prepubertal female rats were administered either ALC (3g/kg) or water via gastric gavage at 07:30hours and at 11:30hours. At 09:00hours, saline or IGF-1 was administered into the third ventricle. Rats were killed at 15:00hours and the medial basal hypothalamus (MBH) was collected for assessment of TGFβ1, IGF-1 receptor (IGF-1R), and Akt. IGF-1 induced TGFβ1 release (p<0.01) from hypothalamic astrocytes in culture, an action blocked by ALC. In vivo, IGF-1 administration caused an increase in TGFβ1 protein compared with controls (p<0.05), an action blocked by ALC as well as a phosphatidylinositol 3 kinase/Akt inhibitor. IGF-1 stimulation also increased both total (p<0.01) and phosphorylated (p)-IGF-1R (p<0.05) protein levels, and phosphorylated (p)-Akt levels (p<0.01), which were also blocked by ALC. This study shows that ALC blocks IGF-1 actions to stimulate synthesis and release of hypothalamic TGFβ1, total and p-IGF-1R, and p-Akt levels further demonstrating the inhibitory actions of ALC on puberty-related events associated with hypothalamic LHRH release.

Exposure of neonatal female rats to bisphenol A disrupts hypothalamic LHRH pre-mRNA processing and estrogen receptor alpha expression in nuclei controlling estrous cyclicity

This study examines the effects of neonatal exposure to the endocrine disruptor bisphenol A (BPA) on the neural network that controls estrous cyclicity. From postnatal day 1 (PND1) to PND7, female pups were injected with vehicle (control) or BPA (BPA.05: 0.05 mg/kg-d, BPA20: 20 mg/kg-d). At PND100 BPA.05-females showed alterations in estrous cyclicity and BPA20-females were incapable of producing an estradiol-induced LH surge. By real-time PCR we determined that hypothalamic expression of mature LH-releasing hormone (LHRH) mRNA was increased in BPA.05 and decreased in BPA20-females. Furthermore, unprocessed intron A-containing LHRH RNA was decreased in the cytoplasm of hypothalamic cells of both groups. Immunohistochemistry revealed that estrogen receptor alpha protein was up-regulated in anteroventral periventricular and down-regulated in arcuate nucleus of both groups. Our results show that BPA permanently disrupts hypothalamic LHRH pre-mRNA processing and steroid receptors expression in nuclei that control estrous cyclicity in adult rats.

Actividad del sistema neuronal LHRH en un modelo animal de retraso del crecimiento

ObjectiveMild and chronic energy restriction results in growth retardation with puberal delay, a nutritional disease known as nutritional dwarfing (ND). The aim of the present study was to assess the profile of hypothalamic luteinizing hormone-releasing hormone (LHRH) release, at baseline and under glutamate stimulation, in ND rats to elucidate gonadotrophic dysfunction. Reproductive ability during refeeding was also studied. Material and methodsAt weaning, 60 male rats were assigned to two groups of 30 animals each: a control and an experimental group. Control rats were fed ad libitum with a balanced rodent diet. The experimental group received 80% of the diet consumed by the control group for 4 weeks. After 4 weeks of food restriction, the ND group was fed freely for 8 weeks. Ten rats from each group were sacrificed every 4 weeks for assays. ResultsAt week 4, body weight and length were significantly diminished in the experimental group vs. the control group (p<0.001). No changes were observed in LHRH baseline release, pulse frequency or amplitude in the experimental group compared with the control group at any time. However, under glutamate stimulation, LHRH release was significantly higher in ND rats than in control rats at week 4 (p<0.05). Refeeding the ND group allowed the rats to reach overall growth and reproductive ability. ConclusionsThe results of the present study suggest that the response to the facilitatory effect of glutamate on LHRH release in post-restricted ND rats is probably related to a lesser central nervous system maturation in relation to their chronological age. The adequate somatic growth and normal reproductive ability attained with refeeding suggest the reversibility of the two energetically costly processes compromised by global, mild and chronic food restriction.

The effect of prolonged stress on the hypothalamic luteinizing hormone-releasing hormone (LHRH) in the anoestrous ewe.

A study was performed to examine the effect of the intermittent long-term (20 min/h daily during 3 consecutive days) electric stress (footshocks) on the hypothalamic LHRH in anoestrous ewe. On the third day, immediately after the last stimulation, the animals were decapitated and the hypothalami and pituitaries were taken for analysis of LHRH and LH by immunocytochemistry; LHRH was also assayed by radioimmunoassay. In the stressed animals the concentration of immunoreactive LHRH (IR-LHRH) and LHRH analysed by radioimmunoassay (RI-LHRH) increased significantly in the median eminence (ME) and the medial preoptic area (MPOA) when compared with the controls. Additionally, IR-LHRH perikarya appeared in the MPOA of stressed animals, whereas they were not seen in the controls. RI-LHRH in the medial basal hypothalamus (MBH) of stressed ewes was markedly lower than in control ones. No significant differences in RI-LHRH concentration were found in the septum between stressed and control ewes. The present study clearly indicates that prolonged stressful stimuli modify LHRH concentration in the discrete areas of the hypothalamus of the anoestrous ewe. It is suggested that these changes are attributed mainly to an inhibition of LHRH release from the ME and a suppression of LHRH transport along neural fibres within the hypothalamus.

Effect of protein deficiency on luteinizing hormone releasing hormone (LHRH), gonadotropin releasing hormone associated peptide (GAP) and luteinizing hormone (LH) immunocytochemistry in the hypothalamus and pituitary gland of prepubertal ewes.

Growing female lambs were fed diets containing 14.2% (standard) or 8.1% (protein restricted) of proteins to determine their effects on puberty and luteinizing hormone releasing hormone (LHRH), gonadotropin hormone associated peptide (GAP), luteinizing hormone (LH) hormonal system. At the end of the experiment (30-34 weeks of age), hypothalamic LHRH, GAP and pituitary LH were analysed by immunocytochemical methods using specific antibodies. Plasma LH were determined by radioimmunoassay at 21 weeks of age. It was found that lowering of the dietary proteins content decreased the concentration of basal plasma LH significantly in lambs of 21 weeks of age. None of the sheep of this group reached sexual maturity at the same time as the animals of the standard group. However, immunoreactive (ir) LHRH neuronal system of protein restricted lambs was normally developed: Numerous irLHRH perikarya, dense network of axons and abundant material stored in the nerve terminals were well visualized in the typical sites of the preoptico-septal area, hypothalamus and the median eminence (ME). Gonadotropin associated peptide (GAP) of the LHRH precursor was present in the same populations of neurons that contained LHRH in the sheep brain. The proportion of pituitary LH-cells was three fold higher in pituitaries of the nutritionally restricted group. They displayed hypertrophy and very strong immunoreaction. These results show that protein deficiency in diets of growing female sheep delays their puberty but does not impair the synthesis and processing of LHRH in the brain neurons and synthesis of LH in pituitary cells.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivoeffect of an luteinizing hormone-releasing hormone analog on vascular endothelial growth factor and epidermal growth factor receptor expression in mammary tumors

Background:The hypothalamic luteinizing hormone-releasing hormone (LHRH) is well known for its role in the control of pituitary gonadotropin secretion and it has demonstrated a direct antiproliferative effect on some cancer cell lines of LHRH and its synthetic analogs. The study was designed to assess whether administration of the LHRH analog (goserelin) has any effect on the expression of the vascular endothelial growth factor (VEGF) and the epidermal growth factor receptor (EGFR) in rats with N-nitroso-N-methylurea (NMU)-induced-mammary tumors “in vivo”Materials and Methods:The animals with tumors were assessed after acute or chronic treatment with goserelin, and in all the animals VEGF and EGFR expression was examined both in plasma and tumor homogenates by enzyme immunoassay.Results:The basal plasma values of VEGF were lower in the healthy control group than in rats with NMU-induced tumors (P = 0.025). Following acute treatment with goserelin, VEGF expression in plasma increased above basal levels after 60 min (P = 0.05) and dropped during chronic treatment. Likewise, in the tumor homogenate the mean VEGF expression was higher at 60 min post-goserelin administration than the basal levels, although VEGF expression then diminished at 90 min. Plasma EGFR expression was higher in rats with NMU-induced tumors than in healthy controls (P<0.01).Conclusions:The results allow us to conclude that goserelin may exert a short-term stimulatory effect on the release of VEGF, as well as a long-term inhibitory effect on VEGF but not EGFR expression.

Rapid modulatory effect of estradiol on acetylcholine‐induced Ca2+ signal is mediated through cyclic‐GMP cascade in LHRH‐releasing GT1‐7 cells

Hypothalamic luteinizing hormone-releasing hormone neurons (LHRH) form the final pathway for the central control of reproduction through the release of LHRH into the pituitary-hypothalamic system. We previously found that LHRH-producing GT1-7 cells respond to acetylcholine (ACh) with an increase in intracellular calcium ([Ca2+]i) through activation of muscarinic receptors. This effect is acutely modulated by 17beta-estradiol in a manner compatible with specific membrane binding sites. Because increasing evidence suggests that second messengers are involved in the rapid action of estradiol, the aim of the present study was to identify the pathway underlying estrogen actions on ACh-induced Ca2+ signals. 8-Bromoguanosine 3',5'-cyclic monophosphate (10 microm) and C-type natriuretic peptide (10 microm) mimicked the effect of estradiol. On the contrary, neither dibutyryl cAMP (100 microm), forskolin (100 nm or 10 microm), or sodium nitroprusside (10 microm) induced any modification of [Ca2+]i in response to ACh. The effect of estradiol on calcium transients was totally blocked by two different cGMP-dependent protein kinase (PKG) inhibitors. In addition, phosphorylation of inositol 1,4,5-triphosphate (IP3) receptor was rapidly induced by estradiol but totally blocked when the cells were pretreated with a PKG inhibitor. We conclude that physiological concentrations of estradiol reduce ACh-induced Ca2+ transients via a mechanism involving a membrane-associated guanylate cyclase, which finally induces a PKG-dependent IP3 receptor phosphorylation that modifies calcium release from the endoplasmic reticulum.

Central and Peripheral Administration of Kisspeptin‐10 Stimulates the Hypothalamic‐Pituitary‐Gonadal Axis

Kisspeptin is the peptide product of the KiSS-1 gene and the endogenous agonist for the GPR54 receptor. Recent evidence suggests the kisspeptin/GPR54 system is a key regulator of the reproductive system. We examined the effect of intracerebroventricular (i.c.v.) and peripheral administration of the active kisspeptin fragment, kisspeptin-10, on circulating gonadotrophins and total testosterone levels in adult male rats. The effect of kisspeptin-10 in vitro on the release of hypothalamic peptides from hypothalamic explants and gonadotrophins from anterior pituitary fragments was also determined. The i.c.v. administration of kisspeptin-10 dose-dependently increased plasma luteinizing hormone (LH) and increased plasma follicle stimulating hormone (FSH) and total testosterone at 60 min postinjection. In a separate study investigating the time course of this response, i.c.v. administered kisspeptin-10 (3 nmol) significantly increased plasma LH at 10, 20 and 60 min, FSH at 60 min and total testosterone at 20 and 60 min postinjection. Kisspeptin-10 stimulated the release of luteinizing hormone-releasing hormone (LHRH) from in vitro hypothalamic explants. Peripheral administration of kisspeptin-10 increased plasma LH, FSH and total testosterone. However, doses of 100-1000 nM kisspeptin-10 did not influence LH or FSH release from pituitary fragments in vitro. Kisspeptin therefore potently stimulates the hypothalamic-pituitary-gonadal axis. These effects are likely to be mediated via the hypothalamic LHRH system.

Leptin-receptor gene transfer into the arcuate nucleus of female Fatty zucker rats using recombinant adeno-associated viral vectors stimulates the hypothalamo-pituitary-gonadal axis.

Fatty fa/fa Zucker rats with a missense mutation in the leptin receptor (OB-R) are obese and infertile with prolonged estrous cycles. To determine whether their reproductive deficits could be corrected by OB-R installation, we employed viral vectors to introduce the OB-R gene into either the arcuate nucleus (ARC) or the paraventricular nucleus (PVN) of the hypothalamus, sites of OB-R expression in wild-type rats. Recombinant adeno-associated viral (rAAV) vectors encoding the human leptin-receptor gene (rAAV-OB-Rb) were microinjected intraparenchymally to produce doxycycline-regulatable OB-R gene expression. Expression of the OB-R gene in the ARC and PVN was verified using reverse transcription-polymerase chain reaction. Expression of OB-R in the ARC, but not in the PVN, resulted in normalization of estrous cycle length, increased ovarian follicular development, and decreased serum progesterone levels. Compared to saline-injected rats, hypothalamic expression of neuropeptide Y (NPY) and pro-opiomelanocortin were decreased in ARC rAAV-OB-Rb-injected rats. Parallel decreases were noted in NPY and beta-endorphin (beta-END) concentrations in the hypothalamus, whereas luteinizing hormone-releasing hormone (LHRH) levels increased. These studies showed that rAAV vectors can be successfully used to install functional OB-R in the hypothalamus for extended periods. The resultant stimulation of the hypothalamo-pituitary-gonadal (HPG) axis in ARC-injected rats was probably brought about by the observed decreases in NPY and beta-END, which inhibit hypothalamic LHRH. Because these changes were seen in ARC-injected, but not in PVN-injected, rats, the results suggest that the ARC may be the primary site where leptin acts to regulate the HPG axis.

Bi-directional associations between galanin and luteinizing hormone-releasing hormone neuronal systems in the human diencephalon

Evidence suggests that galanin plays an important role in the regulation of reproduction in the rat. Galanin is colocalized with luteinizing hormone (LH)–releasing hormone (LHRH) in a subset of LHRH neurons in female rats and galanin-immunoreactive (galanin-IR) nerve terminals innervate LHRH neurons. Recent studies indicate that galanin may control gonadal functions in rats at two different levels: (i) via direct modulation of pituitary LH secretion and/or (ii) indirectly via the regulation of the hypothalamic LHRH release. However, the morphological substrate of any similar modulation is not known in human. In the present series of experiments we first mapped the galanin-IR and LHRH-IR neural elements in human brain, utilizing single label immunohistochemistry. Then, following the superimposition of the maps of these systems, the overlapping sites were identified with double labeling immunocytochemistry and examined in order to verify the putative juxtapositions between galanin-IR and LHRH-IR structures. LHRH and galanin immunoreactivity were detected mainly in the medial basal hypothalamus, in the medial preoptic area and along the diagonal band of Broca. Careful examination of the IR elements in the overlapping areas revealed close, bi-directional contacts between galanin-IR and LHRH-IR structures, which have been verified in semithin plastic sections. These galanin-LHRH and LHRH-galanin juxtapositions were most numerous in the medial preoptic area and in the infundibulum/median eminence of the human diencephalon. In conclusion, the present study is the first to reveal bi-directional juxtapositions between galanin- and LHRH-IR neural elements in the human diencephalon. These galanin–LHRH and LHRH–galanin contacts may be functional synapses, and they may be the morphological substrate of the galanin-controlled gonadal functions in humans.

Close anatomical associations between β-endorphin and luteinizing hormone-releasing hormone neuronal systems in the human diencephalon

Endogenous opiates, such as β-endorphin, inhibit the release of luteinizing hormone (LH) release in the pituitary gland of several species including rat, pig, sheep, and human. Although it is generally believed that β-endorphin influences gonadal functions via the regulation of hypothalamic LH-releasing hormone (LHRH) release, the morphological substrate underlying this regulation in humans remains elusive. In the present series of experiments the β-endorphin-immunoreactive (IR) and LHRH-IR neural elements, utilizing single label immunohistochemistry, were mapped. Following the superimposition of the maps of these systems, the overlapping sites were identified and examined in order to verify the putative juxtapositions between the β-endorphin-IR and LHRH-IR structures. LHRH-IR elements were detected mainly in the medial basal hypothalamus, in the medial preoptic area and along the diagonal band of Broca. β-Endorphin-IR perikarya were observed in the infundibular region/median eminence, whereas β-endorphin-IR axon varicosities were detected periventricularly in the preoptic and tuberal regions, in the medial basal hypothalamus and around the mamillary bodies. Careful examination of the immunoreactive elements in the overlapping areas revealed close contacts between β-endorphin-IR and LHRH-IR structures, which have been verified in semithin plastic sections. These putative β-endorphin–LHRH juxtapositions were most numerous in the medial preoptic area and in the infundibulum/median eminence of the human diencephalon. In conclusion, the present paper is the first study that revealed close juxtapositions between the β-endorphin-IR and LHRH-IR neural elements in the human diencephalon. These β-endorphin–LHRH contacts may be functional synapses, and they may be the morphological substrate of the β-endorphin control on gonadal functions in man.

Effect of adrenergic blockade on the pheromonal restoration of cyclic activity in young oestrogen-primed persistent oestrous female rats.

The effects of adrenergic blockade on pheromonal restoration of cyclic activity were studied in acute oestrogenized persistent oestrous young female rats. Hypothalamic luteinizing hormone-releasing hormone (LHRH) and plasma LH, follicle-stimulating hormone (FSH), oestradiol and progesterone were measured by specific radio-immunoassays, and prolactin by enzyme-linked immunosorbent assay in: (i) young cycling rats; (ii) young persistent oestrous female rats; (iii) young persistent oestrous females treated with nasal sprays of male urine; and (iv) young persistent oestrous females treated with nasal sprays of male urine and injected with saline, propranolol, prazosin or yohimbine. LHRH was low 24 h after oestradiol benzoate injection, increasing up to 15 days later; LH, FSH, oestradiol and progesterone ranged from high values 24 h after oestradiol benzoate injection to low 15 days later; prolactin ranged from low concentration 24 h after oestradiol benzoate injection to high 15 days later. Male urine treatment induced a depletion of LHRH, a rise of LH, FSH and progesterone, pheromonal restoration of cyclic activity and a normal hormonal cyclic pattern. Treatment with prazosin and yohimbine prevented the pheromonal restoration of cyclic activity, the drop of LHRH and the rise of plasma concentration of the studied hormones induced by male urine, while saline or propranolol did not. These results show the hormonal pattern of the pheromonal restoration of cyclic activity in persistent oestrous rats and strongly suggest that alpha-adrenergic inputs to the hypothalamus may be involved in this pheromonal effect.