The distribution of angiotensin II-immunoreactive cells and fibers in the paraventriculo-hypophysial system of the rat.

Angiotensin II (AII)-immunoreactive cell bodies were found in all parts of the paraventricular nucleus of the hypothalamus (PVH) in the normal, colchicine-treated rat. The greatest concentration of cells was found in the posterior part of the magnocellular division of the nucleus, while scattered cells were found in all 5 parts of the parvocellular division. In comparison, the Brattleboro rat showed similar cell staining in parvocellular parts of the PVH, although a substantial decrease in the number of AII-stained cells was found in the magnocellular division. In the normal animal, fiber staining was evident in both laminae of the median eminence. This immunostaining was selectively enhanced in the internal lamina following water deprivation, and was selectively enhanced in the external lamina following adrenalectomy. The Brattleboro rat was similar to the normal animal with regard to staining of the external lamina, but, consistent with the diminished number of immunoreactive magnocellular neurons, little immunostaining in the internal lamina was detected. Unilateral lesions of the PVH selectively diminished staining of fibers and varicosities in the ipsilateral external lamina, while bilateral lesions virtually eliminated staining on both sides. The findings in the Brattleboro rat indicate that specific subpopulations of both parvocellular and magnocellular neurons in the PVH contain an antigen that is immunologically similar to synthetic AII and unrelated to vasopressin or its prohormone.(ABSTRACT TRUNCATED AT 250 WORDS)