The monoaminergic system in the diencephalon of the newt tadpole, Triturus alpestris (Mert). A histofluorescence study.

The distribution of monoamines in the brain of Triturus alpestris tadpoles was investigated with the Falck-Hillarp histofluorescence method. This study concerns especially the diencephalon where is observed the major part of the monoaminergic (MA) neurons. MA fiber tracts are found in the striatum, the septal nucleus and the medial and lateral forebrain bundles of the telencephalon. In the anterior diencephalon cerebrospinal fluid (CSF)--contacting catecholaminergic cells are localized within the preoptic recess organ (PRO) and fibers in the preoptic nucleus. More caudally both CSF-contacting catecholaminergic and serotonergic cells can be demonstrated in the paraventricular organ (PVO) and in the nucleus infundibularis dorsalis (NID). In the hypothalamo-hypophysial tract, numerous catecholaminergic (CA) fibers occur in the median eminence and in the pars intermedia. The origin of these fibers is not elucidated but a participation of the PRO, PVO and NID seems possible. CA cells without contact with the CSF are localized laterally to the PVO, PVO-accompanying cells, and in the nucleus reticularis mesencephali (NRM). The distribution of MA neurons in the brain of Triturus alpestris appears more similar to that of anurans than that of the primitive urodeles.