Semi-quantitative ultrastructural analysis of the localization and neuropeptide content of gonadotropin releasing hormone nerve terminals in the median eminence throughout the estrous cycle of the rat

Prévot, Vincent; Dutoit, Soizic; Croix, Dominique; Tramu, G.; Beauvillain, Jean Claude

doi:10.1016/s0306-4522(97)00537-x

Cited by 63 publications

(79 citation statements)

References 55 publications

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“…Cryostat sections (14 m) were mounted on chrome-alum-gelatincoated slides, air dried, and subjected to fluorescent staining using a procedure described previously (Prevot et al, 1998(Prevot et al, , 2003a. Briefly, the primary antisera were diluted in 0.02 M potassium PBS, pH 7.4, containing 2% heat-inactivated normal goat serum and 0.3% Triton X-100 and incubated overnight at 4°C with sections.…”

Section: Fluorescent Stainingmentioning

confidence: 99%

“…After this preincubation period, tissues were placed in fresh medium containing either 500 M L-arginine (treated group; n ϭ 3), which stimulates the production of NO by endogenous NOS, or not (control group; n ϭ 3) for an additional 30 min incubation period. Explants were subsequently processed for electron microscopy as described previously (Prevot et al, 1998(Prevot et al, , 1999a. Briefly, tissues were fixed by immersion in a mixture of 2% paraformaldehyde, 0.2% picric acid, 0.1% glutaraldehyde, in 0.1 M phosphate buffer, pH 7.4, for 2 hr at 4°C.…”

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

“…Semithin sections (1-2 m thick) were used to progressively approach and identify the portion of the median eminence where the ultrastructural studies were performed, i.e. the area where the pituitary stalk becomes distinct from the base of the hypothalamus but still remains attached to it by the hypophysial portal vasculature system (Prevot et al, 1998(Prevot et al, , 1999a. This area, which does not extend Ͼ20 m, contains high numbers of GnRH fibers.…”

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

“…This area, which does not extend Ͼ20 m, contains high numbers of GnRH fibers. To detect GnRH immunoreactivity, ultrathin sections (80 -90 nm thick) collected on Parlodion 0.8% isoamyl acetate-coated 100 mesh grids (EMS, Fort Washington, PA) were treated using an immunogold procedure described previously (Prevot et al, 1998(Prevot et al, , 1999a. Briefly, after a preliminary treatment with H 2 O 2 (10%; 8 min) and a blocking step in TBS (0.1 M Tris, pH 7.4, 0.15 M NaCl) containing 1% normal goat serum and 1% bovine albumin serum (TBSB) (10 min at room temperature), the grids were floated on a drop of the following reagents and washing solutions: (1) rabbit anti-GnRH (1: 5000) in TBSB for 60 hr at 4°C, (2) TBS to remove excess antibodies (three times for 10 min), (3) colloidal gold (18 nm)-labeled goat antirabbit immunoglobulins (Jackson ImmunoResearch) 1:20 in TBS (0.1 M Tris, pH 7.4, 0.5 M NaCl) for 90 min at room temperature, (4) TBS (three times for 10 min), and (5) distilled water (three times for 10 min).…”

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

“…These end feet engulf neuroendocrine terminals, a structural arrangement that is most evident in the case of nerve endings containing gonadotropin-releasing hormone (GnRH) (Kozlowski and Coates, 1985;Meister et al, 1988), the neuropeptide that controls sexual maturation and adult reproductive function. Through the structural reorganization of their end feet, tanycytes regulate the direct access of GnRH nerve terminals to the vascular wall (King and Letourneau, 1994;Prevot et al, 1998Prevot et al, , 1999a and presumably modulate the release of GnRH into the portal vasculature.…”

Section: Introductionmentioning

confidence: 99%

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Vascular Endothelial Cells Promote Acute Plasticity in Ependymoglial Cells of the Neuroendocrine Brain

et al. 2004

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Glial and endothelial cells interact throughout the brain to define specific functional domains. Whether endothelial cells convey signals to glia in the mature brain is unknown but is amenable to examination in circumventricular organs. Here we report that purified endothelial cells of one of these organs, the median eminence of the hypothalamus, induce acute actin cytoskeleton remodeling in isolated ependymoglial cells and show that this plasticity is mediated by nitric oxide (NO), a diffusible factor. We found that both soluble guanylyl cyclase and cyclooxygenase products are involved in this endothelial-mediated control of ependymoglia cytoarchitecture. We also demonstrate by electron microscopy that activation of endogenous NO release in the median eminence induces rapid structural changes, allowing a direct access of neurosecretory axons containing gonadotropin-releasing hormone (GnRH) (the neuropeptide controlling reproductive function) to the portal vasculature. Local in vivo inhibition of NO synthesis disrupts reproductive cyclicity, a process that requires a pulsatile, coordinated delivery of GnRH into the hypothalamic-adenohypophyseal portal system. Our results identify a previously unknown function for endothelial cells in inducing neuroglial plasticity and raise the intriguing possibility that endothelial cells throughout the brain may use a similar signaling mechanism to regulate glial-neuronal interactions.

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Section: Fluorescent Stainingmentioning

confidence: 99%

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

Section: Assessment Of Ultrastructural Changes Induced By No Productimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vascular Endothelial Cells Promote Acute Plasticity in Ependymoglial Cells of the Neuroendocrine Brain

et al. 2004

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Morphology of the Adult GnRH Neuron

Campbell

2018

The GnRH Neuron and Its Control

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Three‐dimensional properties of GnRH neuroterminals in the median eminence of young and old rats

Yin

Mendenhall

Monita

et al. 2009

J of Comparative Neurology

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The decapeptide GnRH that regulates reproduction in all vertebrates is stored in, and secreted from, large dense-core secretory vesicles in nerve terminals in the median eminence. GnRH is released from these terminals with biological rhythms that are critical for the maintenance of normal reproduction. During reproductive aging in female rats, there is a loss of GnRH pulses and a diminution of the GnRH surge. However, information about the specific role of GnRH nerve terminals is lacking, particularly in the context of aging. We sought to gain novel ultrastructural information about GnRH neuroterminals by performing three-dimensional (3D) reconstructions of GnRH neuroterminals and their surrounding microenvironment in the median eminence of young (4-5 month) and old (22-24 month) ovariectomized Sprague-Dawley female rats. Median eminence tissues were freeze-plunge embedded, and serial ultrathin sections were collected on slot grids for immunogold labeling of GnRH immunoreactivity. Sequential images were used to create 3D models of GnRH terminals. These reconstructions provided novel perspectives into the morphological properties of GnRH terminals, and their neural and glial environment. We also noted that the cytoarchitectural features of the median eminence became disorganized with aging. Quantitative measures showed a significant decrease in the apposition between GnRH terminal membranes and glial cells. Our data suggest reproductive aging in rats is characterized by structural organizational changes to the GnRH terminal microenvironment in the median eminence.

show abstract

Semi-quantitative ultrastructural analysis of the localization and neuropeptide content of gonadotropin releasing hormone nerve terminals in the median eminence throughout the estrous cycle of the rat

Cited by 63 publications

References 55 publications

Vascular Endothelial Cells Promote Acute Plasticity in Ependymoglial Cells of the Neuroendocrine Brain

Vascular Endothelial Cells Promote Acute Plasticity in Ependymoglial Cells of the Neuroendocrine Brain

Morphology of the Adult GnRH Neuron

Three‐dimensional properties of GnRH neuroterminals in the median eminence of young and old rats

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