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Joined 2026-09-21 Message
Incoming links: Median eminence
Hypophyseal portal vein 2026-11-05
A hypophyseal portal vein is a vein connecting the first and second capillary networks of the hypophyseal portal system. The main route carries blood from the median eminence region of the hypothalamus, down the pituitary stalk, to the anterior pituitary. It delivers hypothalamic hormones before their dilution in the wider circulation.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section17.3, Anterior Pituitary and Figure17.9: primary plexus, portal veins and secondary plexus
The word “portal” describes the route: blood leaving one capillary bed reaches another capillary bed before returning to the heart. Here the first bed receives a regulatory message and the second delivers it to responding biological cells. A hypophyseal portal vein is therefore an interconnecting segment, rather than the entire hypophyseal portal system.
A useful example is a pulse of gonadotropin-releasing hormone. In conscious sheep, simultaneous sampling of portal and peripheral blood plasma linked portal GnRH pulses with peripheral luteinizing hormone episodes. Sampling the hypophyseal portal vein route accesses the incoming hypothalamic signal; peripheral sampling detects the resulting pituitary output. That distinction is why the sampling location is part of the experiment, not just a convenient place to draw blood.[ref]
The temporal relationship between gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) secretion in ovariectomized ewes by Iain J. Clarke and James T. Cummins. Abstract: synchronized portal GnRH and peripheral LH secretion in conscious ovariectomized ewes
Median eminence 2026-11-05
The median eminence is a region at the base of the hypothalamus where neurosecretory terminals release regulatory hormones near the first capillary bed of the hypophyseal portal system. It is an interface between hypothalamic neurons and the vascular route to the anterior pituitary. A GnRH terminal here is a site of release; the neuron's soma need not occupy the same location.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Introduction and Abstract: median-eminence neurosecretory interface
Access to the capillaries also depends on neighboring glial cells, including tanycytes. In a 2004 study, female-rat tissue containing the median eminence was incubated for 30 minutes with or without added arginine, a substrate for nitric oxide production. Immunoelectron microscopy identified GnRH-containing terminals. In treated preparations, the investigators observed structural changes bringing terminals into direct contact with the space beside the capillaries. Complementary cell-culture experiments implicated signals from endothelium in glial remodeling.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Abstract; Figure7:500micromolar L-arginine,30min and immunogold localization
The comparison is illuminating because the route is more than a fixed pipe connecting two glands. The arrangement of neurons, glial cells and blood vessels can alter access to the release surface. A microscopic structural observation and a measurement of circulating hormone nevertheless remain different kinds of evidence: proximity alone does not quantify how much GnRH enters the blood.
Nervous tissue 2026-11-05
Nervous tissue, also called neural tissue, is the organized tissue of the nervous system, containing neurons and glial cells. Neurons specialize in communication, including action potentials and signaling between cells. Glial cells maintain the local environment, form insulating myelin in particular locations, and perform other active functions. The brain, spinal cord and peripheral nerves contain different arrangements of these components; a drawing of one isolated neuron is not a complete picture of nervous tissue.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section12.2, Nervous Tissue: neurons, glial cells and their organization
A useful example is the median eminence, where hormone-releasing axon endings interact with tanycytes and blood-vessel endothelium. In a 2004 experiment, investigators compared female-rat tissue explants after 30 minutes with or without 500 micromolar arginine, a precursor for nitric oxide production. Electron microscopy showed identified gonadotropin-releasing hormone terminals close to the vascular boundary after treatment, with fewer intervening tanycyte processes than in controls.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Figure7 and Results: treated versus untreated hypothalamic explants
The observation makes tissue organization experimentally meaningful: changes in the position of a glial cell process can alter a neuron's access to a vascular interface. This specialized arrangement should not be mistaken for the structure of every synapse or every region of nervous tissue.
Sandrine De Seranno 2026-11-05
Sandrine De Seranno investigated signalling between vascular endothelial cells and glial cells in the neuroendocrine brain. A 2004 study combined purified rat median eminence endothelial cells with cultured tanycytes, identifying nitric oxide-dependent changes in the actin cytoskeleton.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Journal of Neuroscience 24, pp. 10353–10363; primary byline and culture experiments
Electron microscopy complemented the culture manipulation: stimulating endogenous nitric oxide release changed how glial endings and GnRH-containing axons approached the vascular surface. The work connected a diffusible signal with altered cellular geometry at a neurovascular interface.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Abstract; nitric oxide signalling and ultrastructural changes
Tanycyte 2026-11-05
A tanycyte is a specialized ependymal cell and glial cell of the hypothalamus. Its body can line the third ventricle, while a long process extends toward underlying tissue. In the median eminence, tanycytic endings surround neurosecretory terminals near blood vessels.[ref]
Vascular endothelial cells promote acute plasticity in ependymoglial cells of the neuroendocrine brain by Sandrine De Seranno and others. Introduction and Figure 1; ventricular cell bodies, long processes and vascular end-feet
In cultured rat tanycytes, signals from endothelial cells altered actin organization through nitric oxide.[ref]