Formaldehyde-induced fluorescence in the telencephalon and diencephalon of the eel (Anguilla anguilla l.). A fluorescence-microscopic and microspectrofluorometric investigation with special reference to the innervation of the pituitary.

In the telencephalon and diencephalon of the eel (Anguilla anguilla L.) formaldehyde-induced fluorescence was studied microscopically and microfluorometrically with special emphasis on the innervation of the pituitary. In the telencephalon fluorescent fibers contained predominantly noradrenaline fluorophores. Fluorescent nuclei could not be established. In the diencephalon fluorescent perikarya were found in: (1) the paraventricular organ (PVO), possessing either dopamine or, to a lesser extent, serotonin fluorophores; (2) the PVO-accompanying group, exhibiting spectral data resembling those of noradrenaline fluorophores; (3) the nucleus hypothalami anterior (NHA), a small paired group of catecholamine-containing cells posterior to the commissura transversa.--The nucleus lobi inferioris exhibited a high density of delicate, most probably dopamine-containing terminals, while fibers surrounding this nucleus contained noradrenaline fluorophores. A high density of fluorescent terminals containing dopamine and/or noradrenaline was found in the habenular complex. Fluorescent terminals in the pituitary contained fluorophores resembling either dopamine or noradrenaline. Fluorescent tracts entered the pituitary from different directions. A rostral, unpaired tract enters the neurointermediate lobe, as also verified experimentally. The rostral pars distalis receives two paired tracts, one from a rostral and one from a dorsal direction. The proximal pars distalis also receives two paired tracts, one from a dorsal and one from a posterior direction.