Morphometric electron-microscopic investigation of the neurons of the supraoptic nucleus in water-loaded, normal and water-deprived rats

The neurons of the supraoptic nucleus (SON) in the rat have been analysed by electron microscopy and morphometry, when the secretion of the antidiuretic hormone was fully suppressed by water loading. The water was supplied through a catheter inserted in the external jugular vein for 1.5, 2.5 and 24 h, respectively. The SON was also examined in normal rats and in rats that had been deprived of water for 72 h. The rats were fixed through chronically implanted catheters, so that at the time of fixation, the animal was uninfluenced by anaesthesia and surgery. The morphology of the granular endoplasmic reticulum and the Golgi complex showed that the water load suppressed the synthetic activity and the water deprivation stimulated it. The total volumes of the vasopressin-containing neurosecretory granules (NG) were 1.6, 2.8 and 5.0 X 10(4) micron3 after a 24-hour water load, in the normal state and after 72-hour water deprivation, respectively. In steady states there was a positive correlation between the secretory activity and the content of NG in the perikaryon.