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Tanycytes and pituicytes: Morphological and functional aspects of neuroglial interaction
Author(s) -
Wittkowski Werner
Publication year - 1998
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/(sici)1097-0029(19980401)41:1<29::aid-jemt4>3.0.co;2-p
Subject(s) - median eminence , neuroscience , perivascular space , biology , ganglionic eminence , neurosecretion , neuroglia , third ventricle , hypothalamus , anatomy , central nervous system , cerebrum
The hypothalamo‐hypophyseal system is supplied with two types of specialized glial cells that interact in neuroendocrine functional dynamics: the tanycytes and the pituicytes. Tanycytes are the dominating glial cells within the median eminence. Similar to radial glia, they extend from the floor of the third ventricle to the neurohemal surface of the median eminence. Pituicytes, as specialized astrocytes, are the main glial cells of the neural lobe. They are in intimate contact with the perivascular space of the sinusoidal vessels. Morphological similarities between the two cell types focus on their interaction with terminal branches of hypothalamic neurons in both regions of the neurohypophysis, the median eminence and the neural lobe. Release of hypothalamic hormones is apparently influenced by pituicytes and tanycytes. For instance, both types of cells are capable of closing or opening the access to the vessels. Thereby, in contrast to the “blood–brain‐barrier” function of astrocytes, pituicytes and tanycytes display “brain–blood‐barrier” functions. Pituicytes are characterized by the expression of specific membrane‐bound receptors for opioids, vasopressin, and β‐adrenoceptors, indicating that they receive input by numerous neuroactive substances. Integration of these incoming signals may result in a regulation of neurosecretion, especially by morphological changes and by modulation of extracellular ion concentrations. Comparable modulatory mechanisms of tanycytes have not yet been elucidated in a convincing manner. Besides possible regulatory functions, tanycytes are considered to possess guiding functions for hypothalamic axons and to be involved in transport mechanisms between ventricle and blood vessels of the portal system. Microsc. Res. Tech. 41:29–42, 1998 © 1998 Wiley‐Liss, Inc.