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Endocrine Functions of Brain Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
PRLR immunoreactive neurons in the rat brain are found in the cerebral cortex (pyramidal cell layer), septal nuclei, and the amygdaloid complex [76]. A dense staining of PRLR is seen in the substantia nigra, habenula and the paraventricular thalamic nucleus. Immunostaining was also seen in the choroid plexus and the subcommissural organ. Within the hypothalamus, PRLRs are found in the suprachiasmatic, supraoptic, paraventricular, dorsomedial and arcuate nuclei; a similar distribution of the PRLR is seen in human and monkey brains.
The Pineal Gland and Melatonin
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
Jerry Vriend, Nancy A.M. Alexiuk
A pineal nerve, or tract, homologous to the optic nerve, has been described in studies of a variety of fish, amphibian, reptile, and avian pineals. Descriptions of synaptic connection of photoreceptor cells with fibers of the pineal tract are well documented,50 but the central projections of the pineal tract have been studied in detail by few investigators. The central projections of the pineal tract reported for these species include the lateral habenular nucleus, pretectal area, and brainstem tegmentum.50–52 In the lamprey, most of the fibers of the pineal tract enter the brain through the posterior commissure. In this species, projections of this tract include the subcommissural organ, pretectal area, thalamus, dorsal hypothalamus, optic tectum, and midbrain tegmentum.53 These central projections of the pineal organ appear to be associated with photosensory (and possibly olfactory) functions in lower species, rather than with the phylogenetic progression to neuroendocrine functions in higher vertebrates.
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.
Eosinophilic globules in a classic ependymoma: evidence of a possible secretory role
Published in Ultrastructural Pathology, 2020
Janice S Ahn, Maureen Petersen, Allan H Friedman, Edward M López, Thomas J Cummings, Anne F Buckley, Giselle Y López
A number of central nervous system (CNS) neoplasms can demonstrate diffuse eosinophilic globules that are thought to represent secretions of the component cell types. Secretory meningiomas are defined by secretory globules called pseudopsammoma bodies, while myxopapillary ependymomas may demonstrate globular eosinophilic structures known as balloons.1 Both pseudopsammoma bodies and balloons are composed of immunophenotypically distinct glycoproteins.2,3 Classic ependymomas are histologically characterized by cells which form perivascular pseudorosettes and occasionally true lumens, known as ependymal rosettes,4 but they are not thought of as having a secretory variant. Here, we report a case of a posterior fossa ependymoma demonstrating numerous glassy eosinophilic globules, the immunophenotype of which did not correspond to similar structures reported in other neoplasms of the central nervous system. Ultrastructural examination revealed a morphology suggestive of the secretory product of the subcommissural organ.
Psychocardiological disorder and brain serotonin after comorbid myocardial infarction and depression: an experimental study
Published in Neurological Research, 2018
Li-Jun Zhang, Mei-Yan Liu, Radhika Rastogi, Jessie N. Ding
There are many studies that support our view, including those of Bulat and Supek [33]. In their study, after an intravenous injection of 5-HT, the 5-HT levels of brain tissue homogenate rise, demonstrating that peripheral blood 5-HT can penetrate the BBB and enter the brain tissue. Young et al. [34] found that SERT expression on BBB’s largest soft membrane vessels was a potential mechanism for peripheral 5-HT access to the CNS. A study by Brust et al. [35] showed that with brain endothelial SERT expression, brain endothelial cells were involved in the release and metabolism of 5-HT. Central 5-HT could directly regulate BBB permeability and cerebral circulation. Nakatani et al. [36] injected 5-hydroxytryptophan (5-HTP) by intravenous injection into intestinal, renal, and liver-removed rats such that 5-HTP could only be converted to 5-HT by the brain tissue rather than the periphery. The results found that whole blood and brain tissue 5-HT levels rose, thus confirming that central 5-HT can pass through the BBB into the peripheral blood. Since 90% of the 5-HT distribution in the periphery is dependent on the intestinal tract, liver, and kidney, this study contradicted previous studies that claimed that brain 5-HT levels have no effect on the periphery. Through this study, after abdominal surgery of the rats, they found that the central 5-HT levels increased through the BBB transported from the periphery. Sharma et al. [37] showed that intravenous injection of 5-HT in rats significantly increased BBB permeability and decreased cerebral blood flow. It was found that 5-HT injection into the dog’s carotid artery and 5-HT injection into the jugular vein of the mice could increase the permeability of BBB by protein tracing the 5-HT receptor on the cerebrovasculature. This increase in permeability of BBB caused by 5-HT was found to be reversible. It can be seen that 5-HT plays an important role in circulation and metabolism in healthy brains. At the same time, we also consider the lack of BBB in certain parts of the CNS, including the pineal gland, neurohypophysis, median eminence, subfornical organ, subcommissural organ, vascular organ of the lamina terminalis, and area postrema as potential access points [38]. Five-HT may be free to enter or leave the brain tissue through the pores of the capillary endothelial cell gaps within these structures. With trimetazidine’s effect on both 5-HT levels seen in this studies as well as on SERT levels in our earlier studies [7,21] could effect BBB permeability and transport of 5-HT from central to peripheral spaces or vice versa.