Postnatal Development of Glial Fibrillary Acidic Protein (GFAP) Immunoreactivity in Pituicytes and Tanycytes of the Mongolian Gerbil (Meriones Unguiculatus)

The postnatal development (day of birth up to the end of the third month) of neurohypophyseal pituicytes and tanycytes of the median eminence (ME) and the medial basal hypothalamus (MBH) was studied immunohistochemically in the Mongolian gerbil (Meriones unguiculatus) with antibodies directed against glial fibrillary acidic protein (GFAP; the major protein subunit of glial filaments). Weak GFAP-immunoreactivity (IR) was scattered in the neural lobe (NL), the ME and the lining of the ventral 3rd ventricle at the first postnatal days. By the end of the second postnatal week, the intensity of the IR had reached a level comparable to that of adult animals. Generally, in the whole neurohypophysis a cytoarchitectonic pattern, which essentially corresponded to adult conditions, was reached around the beginning of the second month. During the first week postnatum, solely perinuclear stainings, mostly unipolar pituicytes with short processes and isolated fibers were discernible in the NL. In the course of the second and third postnatal week, a growing number of the densely arranged pituicytes appeared in form of bi- and multipolar cells. Thickness and length of pituicyte processes, as well as their degree of branching, increased progressively in the first month. The number of GFAP-positive tanycytes in the ventral 3rd ventricle and in the ME most markedly augmented in the first week postnatum. In the MBH, long tanycyte processes emerged from the ventricular lining to cross the arcuate nucleus in large bows, delimiting groups of neurons. Ependymal and subependymal tanycytes in the ME gave rise to radial processes extending to the external zone.(ABSTRACT TRUNCATED AT 250 WORDS)