Fine Structural Changes in Explants of the Neural Lobe of the Rat Hypophysis

To obtain a purified population of pituicytes, pieces of rat neural lobes were dissected free of the pars intermedia, incubated in a variety of media, and fixed at regular intervals between 7 and 56 days of incubation. Many neurosecretory axons survived for up to 21 days without any apparent signs of degeneration. Most axons, however, degenerated and were progressively phagocytosed and subsequently eliminated by pituicytes and microglial cells. Lysed axons that were not eliminated, persisted as dense bodies or paracrystalline inclusions. After 30 days of culture, cluster‐forming pituicytes predominated the explants. Pituicytes underwent morphologic changes such as medium‐dependent decrease or increase of lipid inclusions, Golgi activation, process extension and interdigitation, formation of gap junctions and bundles of intermediate filaments. At the explant surface in contact with the culture medium, pituicytes differentiated into an epithelial layer of ciliated and microvilli‐bearing cells linked by junctional complexes. Long‐term neural lobe explants are a relatively pure source of viable pituicytes and should be useful for further studies on the functional significance of these cells.