The influence of age on the hypothalamo-neurohypophyseal system of the mouse: a quantitative ultrastructural analysis of the posterior pituitary.

A quantitative ultrastructural study of the posterior pituitary was undertaken. The posterior pituitary is the storage of the hormones vasopressin and oxytocin. Female C57BL/Icrfat mice which were under conditions of normal hydration were sampled at 8 and 32 months of age. There was a slight age-related decline in the volume fraction of cellular components with a corresponding increase in perivascular space. The proportion of neurosecretory endings and swellings showing autophagic activity (Dellman type II Herring bodies) increased significantly in the senescent mouse. The total pituicyte population showed a significant decrease in volume fraction, but with a significant increase in electron-dense types. Of the subcellular parameters examined, only the diameter of the neurosecretory granules showed a significant age-related decrease, the volume fraction remaining unaltered. The animals used in this study were from stocks found to be in a constant oestrus-metoestrus-like state unlikely to obscure changes in pituitary morphology. Over-all, the morphology of the posterior pituitary of the senescent female mouse under physiologically defined resting conditions indicates maintenance of the status quo.