Hypothalamic accessory nuclei and their relation to the angiotensinergic and vasopressinergic systems

The existence and colocalization of angiotensin II- and vasopressin-like im munoreactivity in individual magnocellular cell groups of the hypothalamus has been demonstrated by using immunocytochemical methods. These neurosecre tory magnocellular groups consist of the paraventricular nucleus and the su praoptic nucleus, as well as different accessory cell groups. The fibers fr om the neurons of the accessory nuclei project directly to adjacent blood v essels and do not comigrate with the hypothalamo-neurohypophysial fiber pat hway. On the basis of these findings it can be concluded that in the hypoth alamus two different angiotensinergic and vasopressinergic neurosecretory s ystems exist: (1) an intrinsic hypothalamic and (2) a hypothalamo-neurohypo physial system. The distribution of the accessory cell groups in the hypoth alamus is shown in a 3D reconstruction which includes the connection of the se magnocellular nuclei with the vascular system in this area. (C) 1999 Els evier Science B.V. All rights reserved.