EFFECT OF THE PHOTOPERIOD AND ADMINISTRATION OF

EDITH PEREZ ROMERA1,; FABIAN MOHAMED; TERESA FOGAL; SUSANA DOMINGUEZ; RAMON PIEZZI; LUIS SCARDAPANE

ANATOMICAL RECORD

John Wiley & Sons, Inc.

Año: 2009

0003-276X

The pituitary pars tuberalis (PT) is a glandular zone exhibiting well-defined structural 3 characteristics. Morphologically, it is formed by specific secretory cells, folliculostellate 4 cells, and migratory cells coming from the pars distalis. The purpose of this work was to 5 investigate differences in specific cellular characteristics in the PT of viscachas captured 6 in summer (long photoperiod) and winter (short photoperiod), as well as the effects of 7 chronic melatonin administration in viscachas captured in summer and kept under long 8 photoperiod. In summer, the PT-specific cells exhibited cell-like characteristics with an 9 important secretory activity and a moderate amount of glycogen. In winter, the PT10 specific granulated cells showed ultrastructural variations with signs of a reduced 11 synthesis activity. Also, PT showed a high amount of glycogen and a great number of 12 cells in degeneration. After melatonin administration, the ultrastructural characteristics 13 were similar to those observed in winter, but the amount of glycogen was higher. These 14 results suggest possible functional implications as a result of morphological differences 15 between long and short photoperiods, and are in agreement with the variations of the 16 pituitary-gonadal axis, probably in response to the natural photoperiod changes through 17 the pineal melatonin. The ultrastructural differences observed in PT after melatonin 18 administration were similar to those observed in the short photoperiod, thus supporting 19 the hypothesis that these cytological changes are induced by melatonin.