China
Africa
Explore chapters and articles related to this topic
The Dorsal Vagal Complex Forms a Sensory-Motor Lattice: The Circuitry of Gastrointestinal Reflexes
Published in Sue Ritter, Robert C. Ritter, Charles D. Barnes, Neuroanatomy and Physiology of Abdominal Vagal Afferents, 2020
T.L. Powley, H.-R. Berthoud, E.A. Fox, W. Laughton
The area postrema should be considered an element in the vagal lattice. As one of the circumventricular organs, the area postrema serves to transduce inputs not obviously represented in the afferent supply to the NST. Lying outside the blood-brain barrier, the area postrema has access to hormonal and metabolic stimuli in the blood as well as access to humoral factors in the cerebrospinal fluid. In effect, the area postrema constitutes the vagal trigone’s window on the fluxes of circulating hormones, peptides, and metabolites that have the potential to (and in several cases have been shown to) modulate the expression of the digestive reflexes.
Neural Control of Adenohypophysis
Published in Paul V. Malven, 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.
Brainstem and Cardiovascular Regulation
Published in David Robertson, Italo Biaggioni, Disorders of the Autonomic Nervous System, 2019
Ching-Jiunn Tseng, Che-Se Tung
The area postrema (AP) is a circumventricular organ lying in the midline dorsal surface of the caudal medulla oblongata. The AP has been observed in all mammalian species and is characterized by an extremely rich capillary plexus (Roth and Yamamoto, 1968). The capillaries have an unusually weak blood-brain barrier which allows neural elements in the AP to be directly exposed to substances born in the peripheral circulation (Dempsey, 1973). Furthermore, evidence exists that portions of the AP are bathed in cerebrospinal fluid from the overlying fourth ventricle (Krisch and Leonhardt, 1987). The AP is closely adjacent to other structures with known cardiovascular function, including the NTS, dorsal motor nucleus of the vagus, and the A2 catecholaminergic cell group.
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.
Complications of levodopa therapy in Parkinson’s disease
Published in Expert Opinion on Orphan Drugs, 2019
Jordan Dubow, C. Warren Olanow
Aside from the well-defined motor complications, levodopa use is also associated with a series of other adverse events. These include dopaminergic and neuropsychiatric side effects. Dopaminergic side effects include nausea, vomiting, dizziness, and orthostatic hypotension [20,48].These likely relate to activation of dopamine receptors in the area postrema, which is not protected by the blood brain barrier. Levodopa is typically administered with a decarboxylase inhibitor to prevent the peripheral accumulation of dopamine, and this has dramatically reduced the risk and the severity of dopaminergic side effects. When these do occur, they are typically mild and transient, and can be further minimized with a slow titration scheme, taking levodopa with food, and on rare occasions adding additional doses of carbidopa.
Olmesartan combined with renal denervation reduces blood pressure in association with sympatho-inhibitory and aldosterone-reducing effects in hypertensive mice with chronic kidney disease
Published in Clinical and Experimental Hypertension, 2019
Masaaki Nishihara, Ko Takesue, Yoshitaka Hirooka
OLM monotherapy decreased BP, uNE excretion, and TBARS levels in the hypothalamus in hypertensive mice with CKD. We selected a dose of 10mg/kg per day of OLM, because this dose is commonly used to reduce BP in experimental hypertension models (21,43). The findings of the present study indicate that OLM could inhibit SNA by suppressing oxidative stress in the hypothalamus in hypertensive CKD mice. In clinical trials, OLM enhances BP-lowering effects by improving renal ischemia in hypertensive CKD patients with potentially increased SNA (30), which supports the findings of the present study. The blood–brain barrier might prevent systemically administered OLM from acting on the brain, but previous reports demonstrated that OLM acts not only in the peripheral vasculature but also within the brain (17,21). One possible pathway by which orally administered OLM acts on AT1 receptors is through regions that lack a blood–brain barrier, such as the subfornical organ and circumventricular organ or area postrema, thereby inhibiting AT1 receptors within the brain through neural pathways to the hypothalamus (49). The effects of OLM on central SNA might contribute to these preferable effects in CKD mice in the present study.