Morphological and immunocytochemical characterization of electrophysiologically investigated neurons in the PVN of the rat

This study was carried out to characterize angiotensin II (ANG II) sensitiv e neurons in the hypothalamic paraventricular nucleus (PVN) of the rat. An approach was chosen in which a combination of an electrophysiological, a mo rphological, and an immunocytochemical method was focused on one single neu ron. The cell's reaction to an application of ANG II and its specific antag onist Losartan (Dup753) was investigated using the technique of intracellul ar recording inside 450-mu m-thick brain slices. A final injection of a flu orescent dye labelled the neurons. Optical sections were taken through the marked cells by a confocal laser-scanning microscope and made into a three- dimensional cell model on a computer. One-micrometer thin sections were cut from the thick slice at the level of the electrophysiologically characteri zed and marked cell body for immunocytochemical tests with different antibo dies. Our results show an example of such a neuron inside the PVN excited b y ANG II. It was possible to block this excitation with the specific ANG II receptor subtype 1 (AT(1)) antagonist Losartan. The result indicated that the ANG II reaction was mediated by the AT(1) receptor subtype. Immunocytoc hemical studies show that this ANG II-sensitive neuron contains ANG II but no vasopressin. The combination of the results enables us to gain improved information on interactions of peptidergic systems. (C) 2000 Published by E lsevier Science B.V. All rights reserved.