Morphometry of individual capillary beds in the hypothalamo-neurohypophysial system of rats.

Unusually high capillary densities, volumes, and surface areas were revealed by morphometric analysis of the hypothalamic paraventricular nuclei (magnocellular and parvocellular divisions), supraoptic nuclei, and pituitary neural lobe of Long-Evans and Brattleboro rats. Capillaries of the magnocellular division of the paraventricular nucleus were greater in number, but smaller in diameter, than those in the parvocellular division. Expressed per unit area or volume, capillary dimensions in the hypothalamo-neurohypophysial system of Brattleboro rats were the same as in Long-Evans rats.