abstract
- The density of synaptophysin (SN)-immunoreactivity (IR) was examined in pituitary glands of aging male Sprague-Dawley rats. SN-IR was observed as dense dots among endocrine cells of the intermediate lobe, while the neural lobe contained numerous, highly dense immunopositive regions. Some anterior lobe secretory cells contained SN-IR within the cytoplasm, suggestive of the presence of the protein in secretory granules, but no dot-like staining was observed between endocrine cells of that region. A quantitative analysis of the dot-like SN-immunostaining within the intermediate lobe found that tissue from groups of rats aged 13 months, or 15-17 months, contained significantly fewer SN-immunopositive areas than did tissues from 8-month-old animals. Diminished SN immunostaining is suggestive of reduced numbers of synapses in the intermediate lobe, which may lead to alterations in regulation of pituitary hormone secretion from endocrine cells in the older animals.