Immunocytochemical study of angiotensin-II fibres and cell bodies in the brainstem respiratory areas of the cat.

The distribution of fibres and cell bodies containing angiotensin-II in brainstem respiratory nuclei was studied using an indirect immunoperoxidase technique. In order to visualize immunoreactive perikarya, intracerebral injections of colchicine were carried out. The richest cluster of immunoreactive perikarya was localized in the Bötzinger complex and Kölliker-Fuse areas, whereas in the nucleus ambiguus and nucleus retroambiguus a moderate density of cell bodies was observed. The nucleus tractus solitarius (ventrolateral portion) and the nucleus parabrachialis medialis had the lowest number of immunoreactive neurons. Angiotensin-II containing fibres were abundant in the nucleus parabrachialis medialis, Bötzinger complex and Kölliker-Fuse area, and scarce in the nuclei tractus solitarius (ventrolateral part), ambiguus and retroambiguus. Moreover, in the dorsal motor nucleus of the vagus a dense network of immunoreactive fibres and a large number of cell bodies were observed. The presence of angiotensin-II in respiratory areas suggests a role for this octapeptide in controlling respiration.