Glial somatostatin-14 expression in the rat pituitary intermediate lobe: apossible neurotrophic function during development?

Somatostatin-14 was first detected on gestational day 17 in radially-orient ed, bipolar cells spanning the width of the intermediate lobe of the rat pi tuitary. Cells were prominent, and constituted approximately 50% of the lob e area. The presence of vimentin, the cellular shape, and the localization identified these cells as glia. At postnatal day 6, somatostatin-14 and vim entin staining appeared in stellate-shaped cells. This is in agreement with the change from bipolar to stellate shape these glia undergo after the ons et of innervation ([13] Gary et al. Int. J. Devl. Neurosci. 13, 555-565, 19 95). Glia were more abundant, relative to melanotropes, throughout embryoni c and early postnatal development compared to adulthood. Reverse transcript ion-polymerase chain reaction data showed a high level of prosomatostatin m RNA in the intermediate lobe: compared to the anterior and neural lobes fr om postnatal day 2 animals, and a significant drop in intermediate lobe con tent in the adult. The correlation between the number of glia and high expr ession of somatostatin in neonatal relative to adult tissue, together with the close apposition of incoming axons to the abundant, radially oriented g lia during innervation of the lobe, support a neurotrophic function of glia -derived somatostatin. Published by Elsevier Science Ltd on behalf of ISDN.