<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Medial Eminence</th>
</tr>
<tr>
<td class="label">Category</td>
<td>Cell Types</td>
</tr>
<tr>
<td class="label">Brain Region</td>
<td>Hypothalamus</td>
</tr>
<tr>
<td class="label">Neuron Type</td>
<td>Neuroendocrine/Portal neurons</td>
</tr>
<tr>
<td class="label">Species</td>
<td>Human, Mouse, Rat</td>
</tr>
<tr>
<td class="label">Circumventricular Organ</td>
<td>Yes (lacks blood-brain barrier)</td>
</tr>
<tr>
<td class="label">Taxonomy</td>
<td>ID</td>
</tr>
<tr>
<td class="label">Cell Ontology (CL)</td>
<td>[CL:4023035](https://www.ebi.ac.uk/ols4/ontologies/cl/classes/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCL_4023035)</td>
</tr>
<tr>
<td class="label">Marker</td>
<td>Cell Type</td>
</tr>
<tr>
<td class="label">Vimentin</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">GFAP</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">OATP1C1</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">MCT8</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">Leptin Receptor</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">Dopamine</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">Somatostatin</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">GnRH</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">CRH</td>
<td>Neuronal terminals</t
...<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Medial Eminence</th>
</tr>
<tr>
<td class="label">Category</td>
<td>Cell Types</td>
</tr>
<tr>
<td class="label">Brain Region</td>
<td>Hypothalamus</td>
</tr>
<tr>
<td class="label">Neuron Type</td>
<td>Neuroendocrine/Portal neurons</td>
</tr>
<tr>
<td class="label">Species</td>
<td>Human, Mouse, Rat</td>
</tr>
<tr>
<td class="label">Circumventricular Organ</td>
<td>Yes (lacks blood-brain barrier)</td>
</tr>
<tr>
<td class="label">Taxonomy</td>
<td>ID</td>
</tr>
<tr>
<td class="label">Cell Ontology (CL)</td>
<td>[CL:4023035](https://www.ebi.ac.uk/ols4/ontologies/cl/classes/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCL_4023035)</td>
</tr>
<tr>
<td class="label">Marker</td>
<td>Cell Type</td>
</tr>
<tr>
<td class="label">Vimentin</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">GFAP</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">OATP1C1</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">MCT8</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">Leptin Receptor</td>
<td>Tanycytes</td>
</tr>
<tr>
<td class="label">Dopamine</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">Somatostatin</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">GnRH</td>
<td>Neuronal terminals</td>
</tr>
<tr>
<td class="label">CRH</td>
<td>Neuronal terminals</td>
</tr>
</table>
Introduction
Medial Eminence is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
The Medial Eminence (ME) is a circumventricular organ located in the floor of the third ventricle that lacks a blood-brain barrier and serves as a gateway for neuroendocrine communication between the brain and pituitary gland. This specialized structure plays critical roles in hypothalamic-pituitary axis regulation, metabolic sensing, and serves as a neural stem cell niche with significant implications for neurodegenerative diseases[@rodrguez2005][@prevot2010].
Overview
<!-- multi-taxonomy-enrichment -->
Multi-Taxonomy Classification
Taxonomy Database Cross-References
Morphology & Electrophysiology
- Morphology: lateral ganglionic eminence derived neuron (source: Cell Ontology)
- Morphology can be inferred from Cell Ontology classification
External Database Links
- [Cell Ontology (CL:4023035)](https://www.ebi.ac.uk/ols4/ontologies/cl/classes/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FCL_4023035)
- [OBO Foundry (CL:4023035)](http://purl.obolibrary.org/obo/CL_4023035)
- [Allen Brain Cell Atlas](https://portal.brain-map.org/atlases-and-data/bkp/abc-atlas)
- [CellxGene Census](https://cellxgene.cziscience.com/)
- [Human Cell Atlas](https://www.humancellatlas.org/)
Anatomy and Histology
Gross Anatomy
The medial eminence is located in the infundibular region of the hypothalamus, forming the floor of the third ventricle. It appears as a prominent bulge that connects the hypothalamus to the posterior pituitary gland. The ME is bounded laterally by the arcuate nucleus and superiorly by the ventromedial hypothalamus[@bleier1972].
Microscopic Structure
The medial Eminence contains several specialized cell types and structures:
Tanycytes
Tanycytes are specialized ependymal cells that line the ventricular surface and extend long processes into the underlying brain parenchyma. These cells are classified into two main subtypes[@akmel2022][@goodman2015]:
- α-tanycytes: Located primarily in the dorsal ME, with processes extending to the median eminence outer layer
- β-tanycytes: Found predominantly in the ventral ME, with processes terminating on portal capillaries
Tanycytes express distinctive molecular markers including vimentin, GFAP, and various thyroid hormone transporters (OATP1C1, MCT8). They possess tight junctions at their apical surface, creating a barrier between the cerebrospinal fluid and the underlying tissue[@brightman1969].
Herring Bodies
Herring bodies are axonal swellings from hypothalamic neurosecretory neurons that contain dense core vesicles filled with neurohormones. These structures store and regulate the release of hypothalamic releasing and inhibiting hormones into the portal capillary system[@dellmann1971].
Portal Capillary System
The median eminence contains an extensive portal capillary network that connects the hypothalamic nuclei to the anterior pituitary. This portal system allows for rapid, direct communication without entering the systemic circulation[@page1977].
Blood-Brain Barrier Properties
Unlike most brain regions, the medial Eminence lacks a functional blood-brain barrier (BBB), making it a circumventricular organ. This property allows[@weindl1973]:
- Direct sensing of blood-borne molecules (hormones, cytokines, nutrients)
- Gateway for neuroendocrine signaling
- Potential route for drug delivery to the CNS
Molecular Markers
The medial Eminence expresses a distinctive set of molecular markers[@roa2011][@fliers1994]:
Normal Physiological Functions
Neuroendocrine Regulation
The medial Eminence serves as the primary gateway for hypothalamic-pituitary communication[@guillemin1966][@harris1978]:
Portal System Function: Direct vascular connection between hypothalamic neurons and anterior pituitary endocrine cells
Hormone Transport: Enables rapid delivery of releasing/inhibiting factors to the pituitary
Feedback Sensing: Allows hypothalamic neurons to detect circulating hormone levelsHypothalamic Hormones Released via ME
- Thyrotropin-releasing hormone (TRH): Stimulates TSH and prolactin release
- Somatostatin (SST): Inhibits growth hormone release
- Dopamine (DA): Inhibits prolactin secretion
- Gonadotropin-releasing hormone (GnRH): Stimulates LH/FSH release
- Corticotropin-releasing hormone (CRH): Stimulates ACTH release
- Growth hormone-releasing hormone (GHRH): Stimulates GH release
Tanycyte Functions
Tanycytes in the medial Eminence perform multiple critical functions[@rodrguez2010][@garcia2016]:
Barrier Regulation: Gatekeeping between CSF and blood, controlling molecular passage
Transport: Mediate thyroid hormone, leptin, and glucose transport into the brain
Neurogenesis: Serve as neural stem cells, capable of generating new neurons
Energy Sensing: Communicate metabolic state to hypothalamic regulatory centers
Receptor Expression: Express receptors for hormones and nutrients (leptin, insulin, thyroid hormone)The medial Eminence is critically involved in energy homeostasis[@balland2014][@sleiman2019]:
- Leptin Signaling: Tanycytes transport leptin from the blood to hypothalamic neurons
- Glucose Sensing: Detect blood glucose levels and modulate feeding behavior
- Thyroid Hormone Regulation: Control CNS thyroid hormone availability
- mTOR Pathway: Integrate nutritional signals via mechanistic target of rapamycin
Role in Neurodegenerative Diseases
Alzheimer's Disease
The medial Eminence shows significant pathology in Alzheimer's disease (AD)[@braak2012][@scheltens2016]:
Tau Pathology
- Tanycytes accumulate hyperphosphorylated tau protein
- Disruption of tanycyte barrier function
- Impaired thyroid hormone transport to the brain
- Correlation with neurofibrillary tangle distribution
Thyroid Hormone Dysregulation
- Reduced thyroid hormone transport across the ME
- Contributes to cerebral hypothyroidism in AD
- May accelerate cognitive decline
- Thyroid dysfunction is a known AD risk factor
- Impaired leptin signaling
- Disrupted energy homeostasis
- Contributes to hypothalamic dysfunction
- Links metabolic syndrome to AD pathogenesis
Parkinson's Disease
The medial Eminence is affected in Parkinson's disease (PD)[@jellinger1997][@wakabayashi2007]:
Hypothalamic Involvement
- Lewy body pathology extends to hypothalamic nuclei
- Disrupted neuroendocrine regulation
- Autonomic dysfunction originates partly from ME pathology
Sleep-Wake Cycle Disruption
- Altered ME function affects circadian regulation
- Contributes to REM sleep behavior disorder
- Sleep disturbances precede motor symptoms
Autonomic Dysregulation
- Impaired cardiovascular control
- Gastrointestinal dysfunction
- Thermoregulatory abnormalities
Huntington's Disease
Hypothalamic pathology in Huntington's disease (HD) involves the medial Eminence[@van2019][@politis2008]:
- Loss of orexin/hypocretin neurons
- Metabolic disturbances
- Sleep disorders
- Early hypothalamic dysfunction
Multiple System Atrophy
MSA involves autonomic nuclei in the hypothalamic region[@wenning2004]:
- Cardiovascular dysregulation
- Urinary dysfunction
- Sleep architecture disruption
Transcriptomic Profile
Single-cell RNA sequencing has identified distinct cell populations in the medial Eminence[@chen2017][@romanov2020]:
α-tanycytes: Dorsal region, neural stem cell properties
β-tanycytes: Ventral region, barrier function
Neuronal terminals: Neurosecretory axons
Endothelial cells: Portal vasculature
Pericytes: Capillary support
Microglia: Immune surveillanceTherapeutic Implications
Drug Delivery
The lack of blood-brain barrier makes the medial Eminence a potential target for CNS drug delivery[@thorne2004][@dhuria2010]:
- Macromolecule Delivery: Proteins, peptides, and antibodies may access CNS
- Neurodegenerative Therapies: Direct delivery of disease-modifying compounds
- Pituitary Tumors: Access to pituitary via portal system
- Gene Therapy: Potential route for viral vector delivery
Hormone-Based Therapies
Thyroid Hormone Therapy
- Levothyroxine treatment considerations
- T3/T4 transport modulation
- Targeting tanycyte function
- Leptin analog therapy
- mTOR inhibitors
- Metabolic disease management
Regenerative Medicine
The neural stem cell properties of tanycytes offer therapeutic potential[@xie2019]:
- Endogenous neurogenesis activation
- Cell replacement strategies
- Tissue repair mechanisms
Research Directions
Current research focuses on several key areas[@lee2020][@rizzoti2021]:
Tanycyte Biology: Understanding stem cell properties and regeneration
Blood-CSF Barrier: Dynamics of molecular transport
Metabolic Sensing: Integration of nutritional and hormonal signals
Disease Mechanisms: Role in neurodegeneration progression
Therapeutic Targeting: Drug delivery and regenerative approaches
Aging: Age-related changes in ME functionSee Also
- [Hypothalamus](/brain-regions/hypothalamus)
- [Circumventricular Organs
- [Thyroid Hormone Signaling](/mechanisms/circumventricular-organs](/content/mechanisms)
--thyroid-hormone-signaling)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Tanycytes
- [Arcuate Nucleus](/cell-types/arcuate-nucleus-hypothalamus)
](/brain-regions/tanycytes
--arcuate-nucleus)## Background
The study of Medial Eminence has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
- [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
- [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data