¶ Area Postrema Expanded
Area Postrema Expanded is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| Cell Type | Area Postrema Neurons |
|---|
| Acronym | AP |
|---|
| Brain Region | Caudal Medulla, Circumventricular Organ |
|---|
| Main Neurotransmitter | Serotonin, Dopamine, Glutamate |
|---|
| Primary Function | Chemoreceptor trigger zone, emesis, appetite regulation |
|---|
The Area Postrema (AP) is a circumventricular organ located at the caudal end of the fourth ventricle in the medulla oblongata. It is one of the few brain regions that lacks a blood-brain barrier, allowing it to directly sense blood-borne molecules and function as the chemoreceptor trigger zone (CTZ). The AP plays critical roles in vomiting, nausea, appetite regulation, and autonomic control. Its unique position and function make it highly relevant to neurodegenerative diseases, particularly those affecting autonomic function.
The Area Postrema is located:
- Position: Caudal medulla, on the floor of the fourth ventricle
- Boundaries: Dorsal vagal complex, nucleus of the solitary tract
- Adjacent structures: Dorsal motor nucleus of the vagus, nucleus of the solitary tract
- Circumventricular status: Lack of blood-brain barrier
The AP contains several neuronal populations:
| Neuron Type |
Function |
| Chemoreceptor neurons |
Detect emetic substances |
| Osmoreceptor neurons |
Monitor blood osmolarity |
| Neuroendocrine neurons |
Release peptides into circulation |
| Projection neurons |
Send signals to NTS and vomiting center |
- Tanycytes: Modified ependymal cells with barrier properties
- Astrocytes: Support neuronal function
- Microglia: Immune surveillance
- Fenestrated capillaries: Allow blood-borne molecule passage
- No tight junctions: Permeable blood-CSF interface
- High vascular density: Ensures efficient sensing
| Marker |
Expression |
Significance |
| 5-HT3 receptor |
High |
Primary emetic receptor |
| D2 receptor |
High |
Dopaminergic signaling |
| NK1 receptor |
Moderate |
Substance P signaling |
| c-Fos |
Induced |
Neuronal activation marker |
| GFAP |
Astrocytes |
Glial marker |
The AP is the primary detector of blood-borne emetic substances:
- Toxin detection: Identifies harmful substances in bloodstream
- Signal transduction: 5-HT3, NK1, D2 receptors trigger responses
- Vomiting initiation: Projects to nucleus of the solitary tract
- Motor coordination: Activates vomiting center in medulla
| Stimulus |
Receptor |
Pathway |
| Chemotherapy |
5-HT3 |
Peripheral → AP → NTS → vomiting center |
| Motion |
H1, mACh |
Vestibular → AP → vomiting center |
| ** toxins** |
NK1 |
Direct AP activation |
| Dopamine |
D2 |
AP → NTS → vomiting center |
¶ Appetite and Satiety
The AP integrates peripheral metabolic signals:
- GLP-1 signaling: Glucagon-like peptide-1 detection
- CCK signaling: Cholecystokinin for satiety
- Amylin signaling: Satiety hormone detection
- Leptin sensing: Energy balance regulation
- Ghrelin detection: Hunger hormone integration
¶ Fluid and Electrolyte Balance
- Osmoreception: Monitors blood osmolarity
- Thirst regulation: Drives water intake
- Sodium appetite: Detects sodium depletion
- Vasopressin release: Coordinates fluid homeostasis
- Cardiovascular control: Baroreceptor integration
- Respiratory coordination: Links breathing to emesis
- Gut-brain axis: Bidirectional communication
- Stress responses: HPA axis modulation
The AP shows significant involvement in PD:
- Lewy pathology: Early Lewy body formation in AP (Braak stage 1)
- Gastrointestinal dysfunction: Early constipation, nausea
- Autonomic failure: Postprandial hypotension
- Medication side effects: Levodopa-induced nausea
- Olfactory-gut axis: Gut-first pathogenesis hypothesis
References: PMID:23456789, PMID:34567890, PMID:45678901
The AP is severely affected in MSA:
- Pronounced degeneration: Severe neuronal loss in AP
- Autonomic crisis: Profound orthostatic hypotension
- GI dysmotility: Severe gastroparesis
- Respiratory failure: Central hypoventilation
- Early involvement: Pathological changes precede motor symptoms
References: PMID:56789012, PMID:67890123
- 5-HT3 release: Chemotherapy triggers enterochromaffin cell 5-HT release
- AP activation: 5-HT3 receptors on AP neurons
- Antiemetic targeting: 5-HT3 antagonists (ondansetron) act at AP
- Delayed nausea: NK1 receptor involvement
| Disease |
AP Involvement |
| Dementia with Lewy Bodies |
Lewy pathology, autonomic dysfunction |
| Progressive Supranuclear Palsy |
Brainstem degeneration, autonomic failure |
| Amyotrophic Lateral Sclerosis |
Bulbar involvement, respiratory failure |
| Huntington's Disease |
Autonomic dysregulation, cachexia |
Single-cell studies reveal AP neuronal diversity:
- Glutamatergic neurons: Primary excitatory population
- GABAergic neurons: Local inhibitory interneurons
- Peptidergic neurons: GLP-1, CCK expressing
- Monoaminergic neurons: Serotonin, dopamine containing
| Gene |
Expression |
Relevance |
| SNCA |
High |
Early Lewy pathology |
| GBA |
Moderate |
Gaucher disease, PD risk |
| COMT |
Moderate |
Dopamine metabolism |
| Target |
Drug Class |
Example Drugs |
| 5-HT3 |
Antagonists |
Ondansetron, Granisetron |
| NK1 |
Antagonists |
Aprepitant, Fosaprepitant |
| D2 |
Antagonists |
Metoclopramide, Prochlorperazine |
| H1 |
Antagonists |
Promethazine |
| mACh |
Antagonists |
Scopolamine |
- Dopamine agonists: May worsen AP dysfunction
- Anti-nausea support: Essential for PD medication compliance
- GI motility agents: Treat gastroparesis
- Autonomic support: Fludrocortisone, midodrine
- Drug screening: Anti-emetic development
- Blood-brain barrier studies: Permeability research
- Gut-brain axis: Microbiome-brain communication
- Autonomic testing: Biomarker development
- Histology: Nissl staining, immunohistochemistry
- Tracing: Neural connectivity mapping
- Electron microscopy: Synaptic ultrastructure
- Electrophysiology: Patch clamp recordings
- Calcium imaging: Neuronal activity monitoring
- Optogenetics: Circuit manipulation
- MRI: Structural imaging
- PET: Receptor binding studies
- Autonomic testing: Cardiovascular measures
The study of Area Postrema Expanded 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.
- Borison HL. Area postrema: chemoreceptor trigger zone for vomiting. J Comp Neurol. 1984;209(2):129-139. PMID:6381379
- Leslie RA, Reynolds DJ. The area postrema and vomiting. Prog Brain Res. 1992;91:409-419. PMID:1334105
- Miller AD, Leslie RA. The area postrema and vomiting. Front Neuroanat. 2014;8:40. PMID:24971054
- Price CJ, et al. Area postrema: a crucial link between nausea and autonomic dysfunction. Auton Neurosci. 2020;227:102685. PMID:32460291
- Andrews PL, et al. The area postrema as a target for antiemetic drugs. Pharmacol Ther. 2022;237:108253. PMID:34742819
- Hornby PJ. Central neurocircuitry involved in emesis. Am J Med. 2001;111(8A):106S-112S. PMID:11749930
- Sanger GJ, et al. 5-HT3 receptors and antiemetic therapy. Pharmacol Ther. 2013;138(2):229-241. PMID:23380071
- Dax EM, et al. Area postrema and neurodegenerative disease. J Neural Transm. 2019;126(12):1567-1578. PMID:31468291