The Central Connections of Area Postrema Define the Paraventricular System Involved in Antinoxious Behaviors
John Kucharczyk, David J. Stewart, Alan D. Miller in Nausea and Vomiting: Recent Research and Clinical Advances, 2017
Application of the two rules to the connections of area postrema generates the group of nuclei illustrated in Figure 2. For reasons of space, only part of the evidence is given in Table 1. Area postrema projects to several structures in the brain stem (Table 1). The two areas receiving the heaviest labeling in autoradiographic experiments are the nucleus tractus solitarius and the parabrachial nuclei. Nucleus tractus solitarius has brain stem connections similar to, but more extensive than, those of area postrema, but it also projects further rostrally to the forebrain and caudally to the spinal cord. The connections of the other main recipients of postremal input, the parabrachial nuclei, are also shown. Many of the nuclei receiving an input from the area postrema project back to it, but in most cases there are only a few cells involved. The most substantial input is from the paraventricular nucleus of the hypothalamus. From Table 1, the majority of the nuclei belonging to the paraventricular system can be deduced.
Neural Control of Adenohypophysis
Paul V. Malven in Mammalian Neuroendocrinology, 2019
The median eminence is just one of several unique structures in the brain known as circumventricular organs (CVO). These organs, which are also called neurohemal structures, share a common vascular and ependymal organization, which is different from the rest of the brain. As the name denotes, these organs are all located adjacent to some part of a cerebral ventricle. The capillaries in circumventricular organs have a characteristic fenestrated endothelium that probably accounts for the blood-brain barrier being less restrictive in these organs than in most brain tissue. Circumventricular organs are also unique in that their ependymal cells are non-ciliated, whereas ependymal cells in most other regions are ciliated. The diagram in Figure 4-4 shows the location of four different circumventricular organs including the median eminence. The organum vasculosum of the lamina terminalis (OVLT) is located around the rostral projection of the third ventricle above the optic chiasma. The subfornical organ is located on the midline beneath the descending fornix and in contact with the choroid plexus of the third ventricle. The subcommissural organ lines the roof of the third ventricle beneath the posterior commissure and habenula. The three circumventricular organs not illustrated in Figure 4-4 are pars nervosa, pineal gland, and area postrema. The first two of these are covered in detail in Chapters 3 and 10, respectively. The area postrema is located in the roof of the fourth ventricle caudal to the cerebellum.
Anatomy and Physiology of the Autonomic Nervous System
Kenneth J. Broadley in Autonomic Pharmacology, 2017
The vomiting reflex is initiated by irritation of sensory vagal nerve endings in the stomach or duodenal wall by noxious materials in the chyme. These impulses pass to the medullary vomiting centre. Circulating chemicals including drugs such as the cardiac glycosides, nicotine, opiates and chemotherapeutic agents also cause nausea and vomiting by stimulation of the chemosensitive trigger zone (CTZ) in the area postrema in the floor of the fourth ventricle. The blood-brain (BB) barrier in the area postrema is poorly developed and the CTZ is readily reached by these circulating substances. The vomiting centre receives input from the CTZ and from the vestibular apparatus of the inner ear, resulting in motion sickness. The ensuing vomiting reflex is mediated via the vagus nerve, phrenic nerve to the diaphragm and spinal nerves to the abdominal muscles. The upper region of the stomach relaxes while the pylorus contracts and the co-ordinated contractions of the skeletal muscle of the diaphragm and abdominal wall onto the stomach forces the contents out. Nausea and vomiting are associated with other autonomic responses including palor, sweating, salivation, irregular heart rate and hypotension.
Cannabis for cancer – illusion or the tip of an iceberg: a review of the evidence for the use of Cannabis and synthetic cannabinoids in oncology
Published in Expert Opinion on Investigational Drugs, 2019
Ilit Turgeman, Gil Bar-Sela
Emesis results from stimulation of complex reflex pathways controlled by the brain. Neurotransmitters such as dopamine, histamine, acetylcholine, serotonin, and substance P are common targets for anti-emetic medicines, each affecting a distinct aspect of the emetic pathways [18]. Endocannabinoid receptors richly populate these very neuronal tracts, thereby signifying an additional target for treating CINV. The dorsal vagal complex is a region in the brain associated with gastrointestinal function and pathophysiology, and at the root of emesis regulation. This region includes the area postrema, the nucleus of the solitary tract (nTS) and the dorsal motor nucleus of the vagus, and contains vagal outputs in the gastrointestinal tract – all of which contain CB-1 receptors that have demonstrated anti-emetic effects when activated by Δ9-THC [18]. In contrast, serotonin agonists that induce nausea have shown opposite effects on the nTS compared to Δ9-THC [19]. Located just outside the blood-brain barrier in the fourth ventricle of the brain, the area postrema provides direct communication between blood-borne signals such as chemotherapy and the autonomic neurons that elicit emesis [18].
The correlations between steady-state concentration, duration of action and molecular weight of GLP-1RAs and their efficacy and gastrointestinal side effects in patients with type 2 diabetes mellitus: a systematic review and meta-analysis
Published in Expert Opinion on Pharmacotherapy, 2023
Ruoyang Jiao, Chu Lin, Shuzhen Bai, Xiaoling Cai, Suiyuan Hu, Fang Lv, Wenjia Yang, Xingyun Zhu, Linong Ji
The use of heavy-molecular-weight GLP-1RA was associated with a lower risk of GI effects compared with light-molecular-weight GLP-1RA. In fact, the effect of GLP-1RA on CNS remains unclear. The area postrema, located outside the BBB, is a circumventricular organ and an important input of vomit and nausea responses [42]. Circulating GLP-1RA can directly act on the area without the need for crossing the BBB. However, there are other areas in of the brain that are responsible for the inhibition of gastric emptying [43], which may also lead to the GI discomfort including nausea and vomiting. GLP-1RA with light molecular weight may act on receptors in various regions of the bran either peripherally or across the BBB to promote satiety. The stronger effect on CNS by crossing BBB, the higher risk of nausea and vomiting. GLP-1RAs can project to the corresponding regulatory brain areas through the peripheral vagal pathway to inhibit feeding and appetite, or directly act on GLP-1 receptors in the CNS. However, larger GLP-1RAs have a relatively limited effect in promoting weight loss, and their appetite suppression mediated by binding to central GLP-1 receptors may be poor, possibly due to its inability to cross the BBB and are unlikely to enter through periventricular organ leakage [44]. At the same time, the heavy molecular weight of the recipient may prevent other GLP-1RA binding to the receptor. We hypothesized that influence of molecular weight on GI adverse effects was related to high permeability and receptor binding rate, which was not confirmed by relevant studies. And more researches will be needed.
Spontaneous Improvement of Visual Acuity in a 13-Year-Old Boy with Neuromyelitis Optica Spectrum Disorder
Published in Neuro-Ophthalmology, 2019
Keiko Yamaguchi, Takaaki Hayashi, Akiko Kiriyama, Kie Iida, Shoyo Yoshimine, Yoichiro Masuda, Keigo Shikishima, Mitsuko Ariizumi, Genichiro Takahashi, Tadashi Nakano
In NMO, brain lesions are often observed on MRI images. Furthermore, while cerebral lesions are also found in up to 60% of the adult NMO patients, these are usually clinically silent.9,10 In contrast, a study that examined 58 children with NMO found that 66% of these patients had brain lesions while 68% had clinical symptoms that included hiccups, dizziness, hyponatremia, diabetes insipidus, and menstrual irregularities.6,9 Refractory hiccups and vomiting are common concomitant symptoms, and have been found to be associated with the area postrema.11,12 Typically, these symptoms last for several weeks, and precede other clinical signs. Hiccups were also repeatedly observed in the present case, and may be an early sign of the brain lesion. However, in this case, there were no abnormalities noted in the brain and whole-spine MRI.
Related Knowledge Centers
- Autonomic Nervous System
- Brainstem
- Circumventricular Organs
- Sensory Neuron
- Signal Transduction
- Solitary Nucleus
- Medulla Oblongata
- Capillary
- Vascular Permeability
- Hormone