Area postrema

The area postrema is a zirkumventrikuläres organ at the caudal end of the floor of the fourth ventricle, dorsal to the nucleus of the solitary tract ( NTS). Together with other reticular nuclei of the formation and the NTS, it forms the vomiting center. This functional center consists of several core groups and is widely spread around the brainstem down into the medulla oblongata.

Function

Due to the fenestrated capillary endothelium are special neurons located in the area postrema of the chemoreceptor trigger zone with its many different receptors before the blood -brain barrier. The role of these receptors is to respond to toxic substances in the blood as quickly as possible and to allow vomiting as a protective function of the organism.

Clinical Significance

Antiemetics ( medicines for vomiting) are able to block certain receptors in the area postrema. These include, among others:

• Scopolamine inhibits (with seasickness ) muscarinic acetylcholine receptors ( mAChR )
• 5 -HT3 antagonists specifically inhibit the serotonin receptor 5 -HT3.

The many causes that can trigger vomiting (dizziness, pregnancy, cytostatics, increased intracranial pressure, spoiled food, etc. ) suggest a complex neuronal circuitry of the emetic center and the area postrema with higher-level brain centers.

Some drugs ( eg, apomorphine ) act fairly specific in certain dose to the vomiting center and thus may induce vomiting.

• Zirkumventrikuläres organ