Copyrighl © Munksgaard. 1993 J Pineal Res /993 ;/4:78--S3 Joumal of Pineal Research Printed in rhe Unired Srares 01 America-{lff righrs reserved ISSN 0742-3098 Immunohistochemical study of the pineal glial cells in the postnatal development of the rat pineal gland Borregón A, Boya J, Calvo JL, López-Muñoz F. Immunohistoehemieal study of the pineal glial eells in the postnatal development of the rat pineal gland. J. Pineal Res. 1993;14:78-83_ Abstraet: The developmental express ion of the glial antigens, vimentin (VIM), glial fibrillary aeidie protein (GFAP), and S-lOO protein is deseribed in the rat pineal gland from the first postnatal day to adulthood. Thiek VIM immunopositive eell eords forming a network throughout the pineal gland were observed from the first postnatal days_ These eords progressively disappeared during the first post natal month as their eells dispersed into the pineal parenehyma. From 20 to 25 postnatal days, pineal glial eells appeared as isolated star-shaped VIM immunopositive eells. Immunostaining for GFAP and S-lOO protein showed a similar developmental expression pattern. Both antigens appeared later than VIM (15-20 postnatal days) and were restrieted to the pineal glial eells loeated in the proximal third of the gland, close to the pineal stalk. Antonio Borregón, Jesús Boya, Jase Luis Calvo, and Francisco López-Muñoz Department of Histology . Faculty of Medicine , University Complutense , Madrid , Spain Key words : Vimentin,-glial fibrillary acidic protein-S- t 00 protein-glial cells-pineal gland-rat Address reprint requests to Prof. Jesús Boya Vegue, Department of Histology, Faculty of Medicine, University Complutense, 28040 Madrid , Spain Received May 28, 1992; accepted November 11, 1992 . Introduction The pineal gland in rnarnrnals eontains two types of parenehyrnal eells: the rnain eell type or pinealo- eyte, and a seeond cell type variously narned as interstitial eell, type 11 pinealoeyte, etc. [Wolfe, 1965; Arstila, 1967; Pevet, 1977; for review see Vollrath, 1981] . In 1978, et al. showed the presenee of glial fibrillary aeidie protein (GFAP) irnrnunoposi- tive eells within the parenehyrna of the rat pineal gland. These eells were identified as interstitial eells and a glial nature for thern was proposed in rodents. Further studies have eonfirrned the presenee of GFAP in the seeond pineal eeH type of different marnrnals [Huang et al., 1984; Schachner et al., 1984; Calvo et al., 1988; Li and Welsh 1991]. Moreover, the expression of other antigens eonsid- ered as glial eeH rnarkers has been widely doeu- rnented in the seeond pineal eell type in rodents [Sehaehner et al., 1984; Calvo et al., 1988; López- Muñoz et al., 1992]. AH the irnmunohistoehernieal studies so far reported on this pineal eell type were perforrned mainly in adult animals . lnforrnation on the developing immunohistoehernieal eharaeteris- tic s of this eell type is searee. To ouf'lrnowledge, there is only one report describing the postnatal development of GFAP irnmunoreaetivity in the pineal gland of the harnster and gerbil [Li and Welsh, 1991]. In previous investigations, it has been demon- strated that the second pineal cell type expresses three antigens present in glial eells, i .e., the inter- rnediate filament proteins Virnentin (VIM), GFAP, and the cytoplasmic ealcium-binding protein S-lOO et al., 1978; Sehaehner et al., 1984; Calvo et al., 1988; López-Muñoz et al., 1992]. In the present investigation, we studied the developrnental express ion of these three antigens in the rat pineal gland frorn birth to adulthood. Materials and methods Sixty Wistar albino rats of both sexes between 1 day and 6 rnonths old were used in this study. Animals were kept under routine laboratory eonditions, with food and water ad libiturn and in a natural light environment. Four rats at eaeh age stage from 1, 2, 3,5,7, 10, 15,20,25,30,45 days, 2, 3,4, and 6 rnonths were killed by deeapitation under ether anesthesia. Pineal glands were quiekly removed and fixed by irnmersion in Bouin's fixative or Metha- 78