Localization Of Gonadotropin-releasing Hormone Research Articles

Expression of GnRH, Kisspeptin, and Their Specific Receptors in the Ovary and Uterus in Deslorelin-Treated Late-Prepubertal Bitches

In this study, the expression and localization of gonadotropin-releasing hormone (GnRH1) and kisspeptin (KISS1) and their specific receptors in canine ovarian and uterine tissues were investigated after the application of deslorelin acetate (Suprelorin®, 4.7 mg, Virbac, France) in the late prepubertal period. We hypothesized that prolonged treatment of prepubertal dogs with deslorelin would alter the expression of GnRH and kisspeptin genes in the uterus and ovaries. Ovarian and uterine samples of 25 dogs with an average age of 7.8 ± 0.2 months and from mixed breeds were used. Following implant insertion, dogs entered estrus (EST; n = 6); dogs without estrus (N-EST; n = 10) comprised the experimental groups. Nine dogs with placebo implants served as a control (CONT). Ovarian and uterine tissues were investigated for expression of GnRH1, GnRHR, KISS1, and KISS1R/GPR54 mRNA and protein by using IHC and RT-qPCR. In the uterus, expression of GnRH1 significantly decreased in response to deslorelin treatment in the N-EST, compared with the control group. Compared with CONT, KISS1R expression in ovarian samples was significantly lower in the EST group. Uterine protein expression of GnRH1 appeared weaker in N-EST than in CONT. While GnRH1-system members and KISS1 protein were localized in the follicles at various stages and stroma, no or only weak signals were detected for KISS1R in the ovarian samples. Deslorelin-mediated induction of puberty by changing the expression of some of the GnRH and KISS1-system members seems to have an effect on ovarian and uterine functionality. Deslorelin implants can, therefore, not be considered a valuable alternative to induce fertile estrus in late-prepubertal bitches. However, further studies with a larger number of animals are needed to clarify the effect of deslorelin-mediated induction of puberty.

Localization of three forms of gonadotropin-releasing hormone in the brain and pituitary of the self-fertilizing fish, Kryptolebias marmoratus.

The localization of gonadotropin-releasing hormone (GnRH) in the brain and pituitary of the self-fertilizing mangrove killifish Kryptolebias marmoratus was examined by immunohistochemistry and in situ hybridization to understand its neuroendocrine system. The genome assembly of K. marmoratus did not have any sequence encoding GnRH1, but sequences encoding GnRH2 (chicken GnRH-II) and GnRH3 (salmon GnRH) were found. Therefore, GnRH1 was identified by in silico cloning. The deduced amino acid sequence of the K. marmoratus GnRH1 (mature peptide) was identical to that of the medaka GnRH. GnRH1 neurons were detected in the ventral part of the preoptic nucleus by immunohistochemistry and in situ hybridization, and GnRH1-immunoreactive (ir) fibers were observed throughout the brain. GnRH1-ir fibers were in close contact with luteinizing hormone (LH)-ir cells in the pituitary using double immunohistochemistry. GnRH2 neurons were detected in the midbrain tegmentum by immunohistochemistry and in situ hybridization. Although GnRH2-ir fibers were observed throughout the brain, they were not detected in the pituitary. GnRH3 neurons were detected in the lateral part of the ventral telencephalic area by both methods. GnRH3-ir fibers were observed throughout the brain, and a few GnRH3-ir fibers were in close contact with LH-ir cells in the pituitary. These results indicate that GnRH1 and possibly GnRH3 are responsible for gonadal maturation through LH secretion and that all three forms of GnRH function as neurotransmitters or neuromodulators in the brain of K. marmoratus.

Gonadotropin-inhibitory hormone (GnIH) in the amphibian brain and its relationship with the gonadotropin releasing hormone (GnRH) system: An overview

It is well known that the hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) plays an important role as a primary factor regulating gonadotropin secretion in reproductive processes in vertebrates. The discovery of the presence of a gonadotropin-inhibitory hormone (GnIH) in the brains of birds has further contributed to our understanding of the reproduction control by the brain. GnIH plays a key role in inhibition of reproduction and acts on the pituitary gland and GnRH neurons via a novel G protein-coupled receptor (GPR147). GnIH decreases gonadotropin synthesis and release, thus inhibiting gonadal development and maintenance. The GnRH and GnIH neuronal peptidergic systems are well reported in mammals and birds, but limited information is available regarding their presence and localization in the brains of other vertebrate species, such as reptiles, amphibians and fishes. The aim of this review is to compile and update information on the localization of GnRH and GnIH neuronal systems, with a particular focus on amphibians, summarizing the neuroanatomical distribution of GnIH and GnRH and emphasizing the discovery of GnIH based on RFamide peptides and GnIH orthologous peptides found in other vertebrates and their functional significance.

GnIH and GnRH expressions in the central nervous system and pituitary of Indian major carp, Labeo rohita during ontogeny: An immunocytochemical study

Gonadotropin-releasing hormone (GnRH) is the major hypothalamic neuropeptide stimulating gonadotropin secretion in vertebrates. In 2000, gonadotropin-inhibitory hormone (GnIH) was discovered as a hypothalamic neuropeptide that inhibits gonadotropin secretion in birds. Subsequent studies have shown that GnIH is present in the brain of other vertebrates. We show for the first time GnIH immunoreactivity in the central nervous system and pituitary during development of Indian major carp, Labeo rohita and compare it with the localization of GnRH. GnIH and GnRH immunoreactivities were observed from the olfactory system to spinal cord throughout development. In the brain, both neuropeptides were localized in the telencephalon, diencephalon including the preoptic area and rhombencephalon. The localization of GnIH and GnRH in the pituitary suggests that these neuropeptides are involved in the regulation of pituitary hormones by an autocrine manner during development. In addition, the presence of GnIH and GnRH in several other brain regions including the olfactory system suggests their involvement in the regulation of other physiological functions.

Enzymatic removal of polysialic acid from neural cell adhesion molecule interrupts gonadotropin releasing hormone (GnRH) neuron–glial remodeling

There is abundant evidence to prove that the astrocytes are highly dynamic cell type in CNS and under physiological conditions such as reproduction, these cells display a remarkable structural plasticity especially at the level of their distal processes ensheathing the gonadotropin releasing hormone (GnRH) axon terminals. The morphology of GnRH axon terminals and astrocytes in the median eminence region of hypothalamus show activity dependent structural plasticity during different phases of estrous cycle. In the current study, we have assessed the functional contribution of ∞-2,8-linked polysialic acid (PSA) on neural cell adhesion molecule (PSA-NCAM) in this neuronal–glial plasticity using both in vitro and in vivo model systems. In vivo experiments were carried out after stereotaxic injection of endoneuraminidase enzyme (endo-N) near median eminence region of hypothalamus to specifically remove PSA residues on NCAM followed by localization of GnRH, PSA-NCAM and glial fibrillary acidic protein (GFAP) by immunostaining. Using in vitro model, structural remodeling of GnV-3 cells, (a conditionally immortalized GnRH cell line) co-cultured with primary astrocytes was studied after treating the cells with endo-N. Marked morphological changes were observed in GnRH axon terminals in proestrous phase rats and control GnV-3 cells as compared to endo-N treatment i.e. after removal of PSA. The specificity of endo-N treatment was also confirmed by studying the expression of PSA-NCAM by Western blotting in cultures treated with and without endo-N. Removal of PSA from surfaces with endo-N prevented stimulation associated remodeling of GnRH axon terminals as well as their associated glial cells under both in vivo and in vitro conditions. The current data confirms the permissive role of PSA to promote dynamic remodeling of GnRH axon terminals and their associated glia during reproductive cycle in rats.

Localization of gonadotropin-releasing hormone in the central nervous system and a peripheral chemosensory organ of Aplysia californica

Gonadotropin-releasing hormone (GnRH) is a neurohormone crucial for the regulation of reproductive and neural functions in vertebrates. Recent discoveries of GnRH immunoreactivity (IR) in a number of invertebrates raised the possibility that GnRH may be an ancient molecule that had arisen before the emergence of Phylum Chordata. We previously demonstrated the presence of a GnRH IR similar to the mammalian (m) and tunicate I (tI) forms of GnRH in the hemolymph and ovotestis of an opisthobranch mollusk, Aplysia californica; however, the presence of GnRH in the central nervous system (CNS) of A. californica could not be detected with the available antisera against various forms of chordate GnRH. In the present study, we performed immunohistochemistry (IHC) to localize the presence of GnRH in the CNS and a peripheral chemosensory organ, the osphradium, of A. californica. A newly generated antiserum against tI-GnRH revealed the strong expression of GnRH IR in neurons of all CNS ganglia. A notable asymmetry in immunostaining was detected in the left and right abdominal hemiganglia. The CNS is rich in tI-GnRH immunoreactive neurons but lacks mGnRH IR, whereas the osphradium contains abundant mGnRH immunoreactive neurons but lacks tI-GnRH IR. The extract of CNS failed to stimulate the release of LH from mouse pituitary, demonstrating that the A. californica GnRH IR is structurally different from what is required to bind and activate mammalian GnRH receptor. Together, these results indicate the presence of at least two distinct GnRH systems in A. californica. The presence of GnRH in the osphradium is consistent with the long-standing anatomical relationship between GnRH and the chemosensory system observed in vertebrates.

Characterization and localization of gonadotropin-releasing hormone in the brain and pituitary of the three-spined stickleback, Gasterosteus aculeatus

Radioimmunoassay (RIA) studies on highperformance liquid chromatography (HPLC) fractions of brain extracts of the three-spined stickleback, Gasterosteus aculeatus, provided evidence for at least two forms of gonadotropin-releasing hormone (GnRH). One form showed chromatographic and immunological properties similar to that of synthetic salmon GnRH (sGnRH). A second, unidentified form of GnRH eluted in the same position as chicken GnRH I (cGnRH-I); however, it did not cross-react in a cGnRH-I RIA. Furthermore, it cannot be excluded that chicken GnRH II (cGnRH-II) and maybe one other unidentified form are present in the stickleback. The distribution of GnRH in the brain of breeding adult male sticklebacks was studied by use of immunohistochemistry. Two antisera against sGnRH and antisera against mGnRH and cGnRH-II were applied on cryosections and visualized using the peroxidase-antiperoxidase method. Staining patterns were similar after incubations with all four antisera. Immunoreactive fibers were found in most parts of the brain. Three distinct groups of GnRH-immunoreactive perikarya were found in the nucleus olfactoretinalis, in the nucleus anterior periventricularis, and in the nucleus lateralis tuberis. Moreover, weakly stained cells occurred in a periventricular position in the midbrain. The proximal pars distalis of the pituitary, housing the gonadotropic cells, was richly innervated by GnRH-positive fibers. In the pars intermedia and in the rostral pars distalis, immunoreactive fibers were absent.

Characterization and localization of gonadotropin-releasing hormone in the brain and pituitary of the three-spined stickleback, Gasterosteus aculeatus

Characterization and localization of gonadotropin-releasing hormone in the brain and pituitary of the three-spined stickleback, Gasterosteus aculeatus

Immunohistochemical localization of gonadotropin-releasing hormone during implantation in the New Zealand white rabbit

Gonadotropin-releasing hormone was localized immunohistochemically during implantation (gestational days 6 to 14) in the New Zealand White rabbit. During early implantation (days 7 to 9), intense gonadotropin-releasing hormone immunostaining was localized predominantly to the cytoplasm of the nonknob cytotrophoblast with light to moderate staining in the cytoplasm of the syncytiotrophoblast (knob). In later gestation, light to moderate staining of the cytoplasm of the trophoblast at the true placental site was detected. No appreciable change in staining was noted after day 10. Fetal membranes, identified after day 10, showed intense and unchanging immunostaining for gonadotropin-releasing hormone. Obplacental giant cells showed light to moderate nuclear and cytoplasmic gonadotropin-releasing hormone immunostaining. Light to moderate gonadotropin-releasing hormone immunostaining was also noted in the cytoplasm of uterine epithelium and glands. We conclude that immunoreactive gonadotropin-releasing hormone is present in the cytotrophoblast at the time of the earliest embryo-uterine interactions and may play a significant role in implantation and embryo survival.

Ultrastructural localization of gonadotropin-releasing hormone in the porcine gonadotropic cells.

The comparative ultrastructural localization of LHβ, FSHβ and GnRH clearly shows that the granules of the FSH/LH cells contain all three hormones. The separate storage of LH and FSH in a significant number of cells, which in the same granules also display GnRH, may suggest that LH-RH is also FSH-RH and may help to explain the non-parallel release of LH and FSH under some functional conditions.

Localisation of gonadotropin-releasing and thyrotropin-releasing hormones in human brain by radioimmunoassay.

Localization of gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH) in the human brain by radioimmunoassay is reported. The hypothalami and other brain regions were obtained during routine autopsies from 3 22-40 year old females and 12 41-95 year old males. GnRH concentration was highest in the preoptic area (340 pg/mg tissue) and declined progessively toward the caudal region which contained negligible amounts of GnRH. The highest concentrations of TRH were found in the posterior nucleus (158 pg/mg tissue) and the premammillary area. Exceedingly high concentrations of both hormones were in the pituitary stalk (1430 pg/mg and 855 pg/ml tissue for GnRH and TRH respectively). Total content of GnRH in the hypothalamus was 40.5 ng and in the pituitary stalk 58.6 ng. TRH content in the hypothalamus was 61.7 ng and in the pituitary stalk 35 ng. No apparent differences were observed in relation to age or sex. The absence of TRH in the lower 1/3rd of the pituitary stalk implies that it reaches the anterior pituitary by was of the long portal vessels whereas GnRH which is evenly distributed along the whole pituitary stalk and infundibular stem is transported via the long and short portal vessels.

Localization of gonadotropin-releasing hormone (Gn-RH) in the hypothalamus of the mouse by immunoperoxidase technique.

The localization of gonadotropinreleasing hormone (Gn-RH) in the hypothalamus of male and female mice was investigated. Serial paraffin sections were prepared. Rabbit antiserum to synthetic Gn-RH was used as the first reactant in the immunoperoxidase bridge technique. Final reaction products with 3,3' diaminobenzidine were seen by light microscopy. Addition of Gn-RH to the first antibody blocked the staining of immunoreactive tissue Gn-RH. In the hypothalamus of both sexes, the immunoperoxidase technique localized Gn-RH in the perikarya of some arcuate neurons, and throughout the course of numerous tanycytes of the median eminence. Gn-RH staining was also found associated with the organum vasculosum of the lamina terminalis in one of the brains. The releasing hormone was found neither in axons of arcuate neurons nor in other neurons of the hypothalamus. These results suggest that Gn-RH may be synthesized in arcuate neurons, and that tanycytes may provide a major pathway for the secretion of this releasing...