Relationship between arginine vasotocin-like and natriuretic peptide-like immunoreactive structures in the brain of the toad Bufo marinus

The distribution of natriuretic peptide-like immunoreactivity was investigated in the brain of Bufo marinus and compared with arginine vasotocin-like immunoreactivity using fluorescence immunohistochemistry. The antisera used were rabbit anti-porcine brain natriuretic peptide, which recognises the three main structural forms of natriuretic peptides, and guinea-pig antivasopressin, which recognises arginine vasotocin. Natriuretic peptide-like immunoreactive fibres were observed in many regions of the brain, being densest in the preoptic/hypothalamic region of the diencephalon and the interpeduncular nucleus of the mesencephalon. Natriuretic peptide-like immunoreactive cell bodies were observed in the dorsal and medial pallium, the medial amygdala, the preoptic nucleus, the ventral hypothalamus, the nucleus posterodorsalis tegmenti mesencephali, and the interpeduncular nucleus. No natriuretic peptide-like immunoreactivity was seen in the pituitary gland. The distribution of arginine vasotocin-like immunoreactivity was similar to that described previously for other amphibian species. Numerous immunoreactive cell bodies were present in the preoptic nucleus whilst immunoreactive fibres were observed in the preoptic/hypothalamic region as well as in extrahypothalamic regions such as the medial amygdala and the medial pallium. Double-labelling immunohistochemistry revealed no colocalisation of arginine vasotocin-like and natriuretic peptide-like immunoreactivities in the same neural elements. The results suggest that natriuretic peptides and arginine vasotocin have distinct distributions in the brain but that natriuretic peptide-like immunoreactive fibres in the hypothalamus could influence the activity of arginine vasotocin-like immunoreactive cell bodies.     

Immunocytochemical demonstration of GAP-like immunoreactive neuronal elements in the human hypothalamus and pituitary

GnRH-associated peptide (GAP)-like immunonreactive elements located in the human hypothalamus were investigated by PAP immunocytochemistry using specific antiserum against [pro-GnRH (14-69) OH]. Immunoreactive neuronal perikarya were distributed in the MPOA, PVN and infundibular nucleus, with the largest numbers of GAP-like immunoreactive perikarya found in the infundibular nucleus. We also detected the coexistence of GAP-like and GnRH-like immunoreactivities in the same neuronal perikarya in the MPOA by using a double immunolabelling procedure. In addition to the above regions immunoreactive neuronal perikarya were present in the region dorsal to the medial mammillary nucleus. GAP-like immunoreactive fibers were distributed in same areas that immunoreactive perikarya were observed. Many immunoreactive terminals were found adjacent to capillaries in the infundibulum. Immunoreactive dots, presumably terminals, were observed in the posterior pituitary and these were particularly evident along the margin adjacent to the anterior pituitary. The distribution pattern and density of GAP-like immunoreactive neuronal elements are compared with those of other mammalian species. We also compared GAP-like immunoreactive elements with that of GnRH as has been previously observed in the human hypothalamus.     

Immunocytochemical demonstration of GAP-like immunoreactive neuronal elements in the human hypothalamus and pituitary

Summary GnRH-associated peptide (GAP)-like immunoreactive elements located in the human hypothalamus were investigated by PAP immunocytochemistry using specific antiserum against [pro-GnRH (14–69) OH]. Immunoreactive neuronal perikarya were distributed in the MPOA, PVN and infundibular nucleus, with the largest numbers of GAP-like immunoreactive perikarya found in the infundibular nucleus. We also detected the coexistence of GAP-like and GnRH-like immunoreactivities in the same neuronal perikarya in the MPOA by using a double immunolabelling procedure. In addition to the above regions immunoreactive neuronal perikarya were present in the region dorsal to the medial mammillary nucleus. GAP-like immunoreactive fibers were distributed in same areas that immunoreactive perikarya were observed. Many immunoreactive terminals were found adjacent to capillaries in the infundibulum. Immunoreactive dots, presumably terminals, were observed in the posterior pituitary and these were particularly evident along the margin adjacent to the anterior pituitary. The distribution pattern and density of GAP-like immunoreactive neuronal elements are compared with those of other mammalian species. We also compared GAP-like immunoreactive elements with that of GnRH as has been previously observed in the human hypothalamus.     

Neuroanatomical localization of cells containing gonadotropin-releasing hormone messenger ribonucleic acid in the primate brain by in situ hybridization histochemistry

Using in situ hybridization histochemistry, we have mapped the anatomic localization of perikarya containing mRNA that codes for GnRH and GnRH-associated protein (GAP) in the forebrain of four male macaques, Macaca fascicularis. DNA oligomers, with sequences complementary to either the GnRH or the GAP portion of the mRNA sequence, were synthesized and hybridized to paraformaldehyde fixed, coronal sections of the basal forebrain and hypothalamus. GnRH mRNA was found in the same population of cells as those containing GAP mRNA. GnRH/GAP mRNA-containing cell bodies were observed consistently in the medial septal nucleus, the diagonal band of Broca, the medial preoptic area, supraoptic nucleus, and ventromedial-infundibular region. We detected the presence of GnRH mRNA and GAP mRNA within the same neuroanatomic regions previously shown to include perikarya containing immunoreactive GnRH. The ventromedial-infundibular region and the medial preoptic region contained the greatest number of GnRH/GAP mRNA-containing perikarya (37.0% and 22.5%, respectively). The diagonal band contained 21.0% and the supraoptic nucleus 13.0% of the cells, while the medial septum contained the fewest number (6.7%). This study demonstrates the feasibility of using in situ hybridization as a strategy to study the developmental and steroidal regulation of GnRH gene expression in the nonhuman primate.     

Distribution of lamprey gonadotropin-releasing hormone-III (GnRH-III) in brains of larval lampreys (Petromyzon marinus)

Two immunoreactive forms of gonadotropinreleasing hormone (GnRH), lamprey GnRH-I and lamprey GnRH-III, were found in neurons in larval sea lampreys (Petromyzon marinus). Using antisera preferentially directed against either lamprey GnRH-I or-III, dense reaction product was seen in cell bodies in the rostral hypothalamus and preoptic area. Reaction product was also dense in fibers to and within the neurohypophysis, in addition to numerous fibers which projected caudally, beyond the neurohypophysis through the mesencephalon. The majority of immunoreactive GnRH was lamprey GnRH-III, and when lamprey GnRH-I was seen, it was in cells that appeared to contain both forms of GnRH. A small number of cells found in the caudal hypothalamus contained only immunoreactive lamprey GnRH-III, and these may constitute a functional subgroup within the population of GnRH neurons. In animals undergoing metamorphosis there was a large increase in reaction product in all GnRH-containing cells and fibers. A striking change within the distribution of GnRH cells was localized to a distinct group of GnRH-immunoreactive cells (GnRH-I and-III) in the ventral anterior hypothalamic area. These cells were minimally detectable in larvae, but during metamorphosis became densely filled with immunoreactive product in perikarya and distal processes. The results are consistent with the hypothesis that lamprey GnRH-III is an important form of GnRH during the maturation of GnRH cells and fibers, and further indicates that these cells have attained their normal positions in the preoptic area and hypothalamus before metamorphosis.     

A developmental study of the gonadotropin-releasing hormone neuronal system during sexual maturation in the male Djungarian hamster.

The number, morphology, and distribution of gonadotropin-releasing hormone cell bodies were studied in the brain of the male Djungarian hamster during sexual maturation. Males were reared in long days (16L:8D) and were killed at 15, 25, or 40 days of age, before (n = 5), during (n = 4), or after puberty (n = 4), respectively. Brain sections (60 microns) from the rostral olfactory tubercle to the medial basal hypothalamus were processed for GnRH immunocytochemistry. Unipolar and bipolar neurons were immunolabeled for GnRH; both subtypes had smooth cell contours. Analysis of every section from the olfactory tubercle to the arcuate nucleus indicated that at all ages more than 75% of all GnRH-immunoreactive cell bodies were distributed in the diagonal band of Broca, medial preoptic area, lateral preoptic area, and lateral hypothalamic area. GnRH-positive somata were also found in other brain regions, but in each of these areas they represented less than 6% of the total GnRH neuron number. In peripubertal 25-day-old males, during the rapid phase of testes growth, the number of unipolar, but not bipolar, GnRH-labeled cells nearly doubled in the diagonal band of Broca compared to soma numbers in this location in prepubertal 15-day-old males. The same number of unipolar GnRH-stained somata were found in this region in 40-day-old as in 25-day-old hamsters. In the medial preoptic area, a similar doubling of unipolar neuron numbers was observed at 25 days, but by 40 days the number of unipolar immunostained GnRH cells was secondarily reduced to a level comparable to that at 15 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of gonadotropin-releasing hormone immunoreactive systems in the brain of the Senegalese sole, Solea senegalensis

The present paper reports the immunohistochemical distribution of the gonadotropin-releasing hormone (GnRH) structures in the brain of the Senegalese sole, Solea senegalensis. In this study, we have used two antibodies against the salmon GnRH and chicken GnRH-II forms and the streptavidin–biotin-peroxidase complex method. Immunoreactive cell bodies are observed at the junction between the olfactory bulbs and the telencephalon (terminal nerve ganglion cells), in the ventral telencephalon, in the preoptic parvocellular nucleus, and in the synencephalic nucleus of the medial longitudinal fasciculus. GnRH-immunoreactive fibres were found extensively throughout the brain, located in the telencephalon, preoptic area, hypothalamus, hypophysis, optic tectum, midbrain and rhombencephalon. The antisera used in this study against the two GnRH forms exhibited cross-reactivity on the same cell masses and did not allow cell populations expressing different GnRH forms to be discriminated clearly. However, anti-salmon GnRH immunostained the GnRH cells and fibres of the forebrain much more intensely, whereas the anti-chicken GnRH antiserum shows a higher immunoreactivity on synencephalic cells of the medial longitudinal fasciculus.     

Neuroanatomical specificity in the co-localization of aromatase and estrogen receptors

The relative distributions of aromatase and of estrogen receptors were studied in the brain of the Japanese quail by a double-label immunocytochemical technique. Aromatase immunoreactive cells (ARO-ir) were found in the medial preoptic nucleus, in the septal region, and in a large cell cluster extending from the dorso-lateral aspect of the ventromedial nucleus of the hypothalamus to the tuber at the level of the nucleus inferioris hypothalami. Immunoreactive estrogen receptors (ER) were also found in each of these brain areas but their distribution was much broader and included larger parts of the preoptic, septal, and tuberal regions. In the ventromedial and tuberal hypothalamus, the majority of the ARO-ir cells (over 75%) also contained immunoreactive ER. By contrast, very few of the ARO-ir cells were double-labeled in the preoptic area and in the septum. More than 80% of the aromatase-containing cells contained no ER in these regions. This suggests that the estrogens, which are formed centrally by aromatization of testosterone, might not exert their biological effects through binding with the classical nuclear ER. The fact that significant amounts of aromatase activity are found in synaptosomes purified by differential centrifugation and that aromatase immunoreactivity is observed at the electron microscope level in synaptic boutons suggests that aromatase might produce estrogens that act at the synaptic level as neurohormones or neuromodulators.     

GnRH-prohormone-containing neurons in the primate brain: immunostaining for the GnRH-associated peptide

The structure of the prohormone for mammalian gonadotropin releasing hormone (proGnRH) includes the GnRH decapeptide followed by a 56 amino acid GnRH-associated peptide (GAP). In this study, we compared immunostaining of brain neurons and fibers for GAP and GnRH in fetal rhesus monkeys and juvenile baboons. We used antisera against different portions of human and rat GAP (proGnRH 14-24, proGnRH 40-53, and proGnRH 52-66) or against GnRH and the PAP technique. Liquid phase absorption with GAP or GnRH confirmed the specificity of these antisera. Major accumulations of GAP immunoreactive (GAP+) perikarya occurred in the medial septal and preoptic areas and the nucleus of the diagonal band of Broca (44.6% in rhesus, 49.6% in baboon), supraoptic region including the area dorsal to the optic tract (21.9% in rhesus, 23.0% in baboon), and the medial basal hypothalamus (15.7% in rhesus, 16.4% in baboon), especially at the infundibular lip. Occasional cell bodies were scattered throughout the hypothalamic and forebrain regions studied. GAP+ fibers were widely distributed, but formed well-defined pathways such as the periventricular and ventral hypothalamic tract. In addition, GAP+ nerve terminals with various densities occurred in the lamina terminalis, the zona externa of the infundibulum, and behind the infundibular stalk. Fetal rhesus macaques had more GAP+ cell bodies, denser fiber networks, and more distinct pathways than juvenile baboons. However, fiber and terminal immunostaining was somewhat less intense for GAP than GnRH in comparable regions. These results indicate that proGnRH (GAP) is present in the same population of neurons as GnRH in the primate brain. They also suggest that post-translational products of proGnRH are present in perikarya, axons and terminals, and that GnRH and GAP and/or further cleavage products are consecreted into hypophysial portal blood in the primate.     

Estrogen receptor and progesterone receptor-immunoreactive cells are not co-localized with gonadotropin-releasing hormone in the brain of the female mink (Mustela vison)

The distribution of gonadal steroid (estrogen, progesterone) receptors in the brain of the adult female mink was mapped by immunocytochemistry. Using a monoclonal rat antibody raised against human estrogen receptor (ER), the most dense collections of ER-immunoreactive (IR) cells were found in the preoptic/anterior hypothalamic area, the mediobasal hypothalamus (arcuate and ventromedial nuclei), and the limbic nuclei (amygdala, bed nucleus of the stria terminalis, lateral septum). Immunoreactivity was mainly observed in the cell nucleus and a marked heterogeneity of staining appeared from one region to another. A monoclonal mouse antibody raised against rabbit uterine progesterone receptor (PR) was used to identify the PR-IR cells in the preoptic/anterior hypothalamic area and the mediobasal hypothalamus (arcuate and ventromedial nuclei). This study also focused on the relationship between cells containing sex-steroid receptors and gonadotropin-releasing hormone (GnRH) neurons on the same sections of the mink brain using a sequential double-staining immunocytochemistry procedure. Although preoptic and hypothalamic GnRH neurons were frequently in close proximity to perikarya containing ER or PR, they did not themselves possess receptor immunoreactivity. The present study provides neuroanatomical evidence that GnRH cells are not the major direct targets for gonadal steroids and confirms for the first time in mustelids the results previously obtained in other mammalian species.     

Relationship of CRF-immunostained cells and magnocellular neurons in the paraventricular nucleus of rat hypothalamus

The distribution of corticotropin-releasing factor (CRF), vasopressin (VP) and oxytocin (OXY) containing neurons within the magnocellular and parvocellular divisions in the paraventricular nucleus (PVN) of rat hypothalamus is described in brains from normal untreated, colchicine treated and adrenalectomized animals. Double immunostained preparations using glucose oxidase-antiglucose oxidase (GAG) complex combined with PAP complex to visualize two antigens with contrasting colors in the same tissue sections were employed. Separate and distinct populations of cells containing the immunoreactive (ir) elements were seen. Immunostained CRF neurons present in the ventral medial portion of the posterior magnocellular division were juxtaposed to oxytocin-ir perikarya in colchicine treated and adrenalectomized animals. CRF-ir cells were for the most part concentrated in the medial parvocellular component of PVN. An intimate anatomical proximity between CRF-ir and VP-ir perikarya was evident in this medial parvocellular division in brains of adrenalectomized animals; this area is normally VP-ir poor except in the adrenalectomized rats. This extension of VP-ir cells into this CRF rich region and the very close approximation between the two cell bodies suggests potential cell to cell communication following perturbation of the brain-pituitary-adrenal axis. No evidence for the co-existence of two peptidergic systems in the same neuron was apparent in the present study.     

Ontogeny of the pig hypothalamic neurosecretory system with particular reference to the distribution of neurophysin

The immunoperoxidase cytochemical reaction was applied to the localization of neurophysin-containing elements in the fetal and adult pig hypothalamus. In the 60 day fetal pig, cells of the supraoptic nucleus (SON) were the only structues in the hypothalamus in which neurophysin was detected. However, by 87 days the cell bodies in both the SON and paraventricular nucleus (PVN) contained neurophysin-like material. The distribution of immunoreactive material in the 111 day fetal animal was similar to that found in the adult pig. In transverse section of the mature pig the SON exists in two discrete components; an antero-lateral group of cells connected by scattered cells to a smaller postero-medial group. Anteriorly, the PVN appears as a line of cells bordering the third ventricle but as we proceed posteriorly the dorsal aspect expands laterally to give a wedge-shaped group of cells. In mid-sagittal sections, the cells of the PVN are distributed over a wide area of the anterior hypothalamus in a triangular profile. The borders between the SON and PVN became more difficult to define in medial sections than in lateral sections. Continuous gradient polyacrylamide gel electrophoresis was carried out on the neural lobe extracts from fetal, newborn and adult pigs. Proteins with an electrophoretic mobility similar to that of porcine neurophysins-I, -II and -III were present in the newborn and 98 day fetal pig. It is concluded that material immunoreactive with anti-neurophysin serum is present in the hypothalamus of the 60 day fetal pig. Furthermore, at late fetal development and during the postnatal period it is tentatively suggested that the neurophysin present in the pituitaries of these animals is chemically identical with that of adult neurophysin.     

Distribution of FMRFamide-like immunoreactivity in the brain,retina and nervus terminalis of the sockeye salmon parr,Oncorhynchus nerka

Summary Neurons displaying FMRFamide(Phe-Met-Arg-Phe-NH₂)-like immunoreactivity have recently been implicated in neural plasticity in salmon. We now extend these findings by describing the extent of the FMRF-like immunoreactive (FMRF-IR) system in the brain, retina and olfactory system of sockeye salmon parr using the indirect peroxidase anti-peroxidase technique. FMRF-IR perikarya were found in the periventricular hypothalamus, mesencephalic laminar nucleus, nucleus nervi terminalis and retina (presumed amacrine cells), and along the olfactory nerves. FMRF-IR fibers were distributed throughout the brain with highest densities in the ventral area of the telencephalon, in the medial forebrain bundle, and at the borders between layers III/IV and IV/V in the optic tectum. High densities of immunoreactive fibers were also observed in the area around the torus semicircularis, in the medial hypothalamus, median raphe, ventromedial tegmentum, and central gray. In the retina, immunopositive fibers were localized to the inner plexiform layer, but several fiber elements were also found in the outer plexiform layer. The olfactory system displayed FMRF-IR fibers in the epithelium and along the olfactory nerves. These findings differ from those reported in other species as follows: (i) FMRF-IR cells in the retina have not previously been reported in teleosts; (ii) the presence of FMRF-IR fibers in the outer plexiform layer of the retina is a new finding for any species; (iii) the occurrence of immunopositive cells in the mesencephalic laminar nucleus has to our knowledge not been demonstrated previously.     

GnRH及其受体在性成熟前后鲇、黄颡鱼脑、垂体和卵巢中的免疫细胞化学定位

用链霉亲和素 -生物素化过氧化物酶复合物 (StreptAvidinBiotin peroxidaseComplex ,SABC)免疫细胞化学方法 ,使用促性腺激素释放激素 (Gonadotropin releasinghormone ,GnRH)以及促性腺激素释放激素受体 (GnRHR) 2种抗血清对性成熟前后的黄颡鱼 (Pelteobagrusfulvidraco)和鲇鱼 (Silurusasotus)的脑、垂体、卵巢中的免疫活性内分泌细胞进行了免疫细胞化学定位。结果表明GnRH和GnRHR免疫活性在两种鱼的各脑区、垂体、卵巢中均有分布 ;两种鱼在性成熟时它们的下丘脑、垂体和卵巢中的GnRH和GnRHR免疫反应细胞数目和免疫反应强度明显高于性成熟前。本文讨论了GnRH、GnRHR直接或间接参与黄颡鱼和鲇鱼性腺发育成熟调节的可能性及形态学证据。可为下丘脑 垂体 性腺轴、神经 内分泌、GnRH功能的多样性等研究领域提供新的形态学依据。     

Newborn GnRH neurons in the adult forebrain of the ring dove

The preoptic area of the hypothalamus is a key area that produces gonadotrophin-releasing hormone (GnRH). In birds, the chicken GnRH-I-form neurons are responsible for the hypothalamus-pituitary-gonadal system, which controls reproduction. In the ring dove, electrolytic lesion in the adult hypothalamus induces neurogenesis. In this study, we determined whether adult neurogenesis is involved in repairing GnRH neurons, specifically by generating newborn cells exhibiting GnRH-I immunoreactive properties. We selectively applied electrolytic lesions to three different regions of the diencephalon, including the preoptic area, which contains GnRH-I neurons, and identified new cells (BrdU-positive cells) that co-labeled with GnRH-I-immunoreactive cells. The BrdU⁺/GnRH⁺ double labeled cells were then confirmed with confocal laser analysis. In brains of both male and female ring doves we found new neurons at the lesion site of the preoptic region that were GnRH-I immunoreactive. However, the total number of GnRH neurons in the lesioned brains was less than that of sham-lesioned brains. When two other regions of the diencephalon that contain GnRH-I neurons were damaged, no recruitment of new GnRH-I neurons was detected. The rate of neurogenesis depends on the bird's reproductive phase when the lesion was applied. We found BrdU⁺/GnRH⁺ double-labeled cells almost exclusively during the pre-laying phase when birds are engaged in active courtship that leads to egg laying. Our observations suggest that recruitment of GnRH immunoreactive new neurons is restricted to the hypothalamic region and is sensitive to the reproductive stage of the birds.     

Localization of galanin-like immunoreactive structures in the brain of the Senegalese sole, Solea senegalensis

The distribution of galanin-like immunoreactive structures was studied in the brain of the Senegalese sole, Solea senegalensis, using immunohistochemical methods. Periventricular immunoreactive cell bodies were observed in the rostral pole of the preoptic recess, within the pars parvocellularis of the nucleus preopticus parvocellularis. Another galanin-immunoreactive cell population was observed more caudal in the ventromedial hypothalamus, along the medial evaginations of the lateral recess. These cells appear within the cytoarchitectonic limits of the nucleus recessus lateralis pars ventralis. We found an extensive presence of galanin-immunoreactive fibres throughout the entire brain, although the most massive network of fibres was observed in the caudal olfactory bulbs, ventral telencephalon, preoptic area and around diencephalic ventricular recesses. Also, the hypophysis, ventricular mesencephalic area, median reticular formation and viscerosensory rhombencephalon displayed important plexuses of galanin-immunoreactive axons.The widespread distribution of these immunoreactive structures in the brain and pituitary of the Senegalese sole suggests an important role for galanin in neuroendocrine regulation of brain and adenohypophyseal functions.     

Distribution of gonadotropin-releasing hormone-like peptides in the brain during development of juvenile male Rana esculenta

Summary The distribution and density of cell bodies and fibers immunoreactive to GnRH-like peptides were investigated in the brain of male juvenile frogs (Rana esculenta) during postmetamorphic development. An immunohistochemical technique was used, involving antisera raised against 4 variants of GnRH: mammalian GnRH, chicken GnRH-I, chicken GnRH-II and salmon GnRH. A comparison of the immunohistochemical distribution at 8 different developmental stages shows that the maximum density of immunoreactive-GnRH elements, and the full distributional complexity of this system, is attained at the completion of spermatogenesis. Immunoreactive-GnRH cell bodies first appear in the anterior preoptic area during the metamorphic climax, and then appear sequentially in the medial septal area, tegmentum and, lastly, in the retrochiasmatic area and olfactory bulb when immunoreactive-fibers also reach the cerebellum. The GnRH system reacts positively to antisera for all 4 GnRH variants, but immunoreactivity for chicken GnRH-I is the weakest.     

A role for foxd3 and sox10 in the differentiation of gonadotropin-releasing hormone (GnRH) cells in the zebrafish Danio rerio

Gonadotropin-releasing hormone (GnRH) is found in a wide range of vertebrate tissues, including the nervous system. In general, GnRH has two functions: endocrine, acting as a releasing hormone; and neuromodulatory, affecting neural activity in the peripheral and central nervous system. The best understood population of GnRH cells is that of the hypothalamus, which is essential for reproduction. Less well understood are the populations of GnRH cells found in the terminal nerve and midbrain, which appear to be neuromodulatory in function. The GnRH-containing cells of the midbrain are proposed to arise from the mesencephalic region of the neural tube. Previously, we showed that neuromodulatory GnRH cells of the terminal nerve arise from cranial neural crest. To test the hypothesis that neuromodulatory GnRH cells of the midbrain also arise from neural crest, we used gene knockdown experiments in zebrafish to disrupt neural crest development. We demonstrate that decrement of the function of foxd3 and/or sox10, two genes important for the development and specification of neural crest, resulted in a reduction and/or loss of GnRH cells of the midbrain, as well as a reduction in the number of terminal nerve GnRH cells. Therefore, our data support a neural crest origin for midbrain GnRH cells. Additionally, we demonstrate that knockdown of kallmann gene function resulted in the loss of endocrine GnRH cells of the hypothalamus, but not of neuromodulatory GnRH cells of the midbrain and terminal nerve, thus providing additional evidence for separate pathways controlling the development of neuromodulatory and endocrine GnRH cells.     

Short photoperiod-induced gonadal regression: effects on the gonadotropin-releasing hormone (GnRH) neuronal system of the white-footed mouse, Peromyscus leucopus

The peroxidase-antiperoxidase method was used to determine quantitatively the effect of short photoperiod-induced gonadal regression on the immunoreactive gonadotropin-releasing hormone (GnRH) neuronal system of female Peromyscus leucopus. In mice exposed to either long (16L:8D) or short (8L:16D) photoperiod, immunoreactive cell bodies were loosely organized into six groups: olfactory peduncle, diagonal band of Broca, septum, preoptic area (POA), anterior hypothalamus (AH), and basal hypothalamus. The POA and AH contain the largest number of cell bodies, which supply the major GnRH innervation to the median eminence (ME) and several extrahypothalamic brain sites. Exposure to short photoperiod increased the number of immunoreactive cell bodies within the anterior hypothalamus and preoptic area (AHPOA) and also increased the optical density for staining of immunoreactive cell bodies in the AHPOA and olfactory peduncle. The ME of mice exposed to short photoperiod had a higher density of GnRH fibers relative to that of mice exposed to long photoperiod, and the content of GnRH fibers in the rostral ME was correlated with the optical content for immunostaining of cell bodies in the AHPOA. These results are evidence that gonadal regression induced by short photoperiod (mediated by the pineal gland) involves alterations of GnRH neuronal activity. Notably, data from this study are consistent with the hypothesis that suppressed release of GnRH from neurovascular terminals in the ME, rather than lack of availability of the decapeptide, promotes gonadal regression.