Organization of diencephalic and brainstem afferent projections to the lateral septum in the rat.

Ascending diencephalic and brainstem afferents to the lateral septal column were studied by retrograde transport of horseradish peroxidase following microiontophoretic injections in the various subdivisions of the lateral septal area. Predominantly ipsilateral cells, of which several coincide with reported monoaminergic cell groups, appeared in the preoptic area, several hypothalamic nuclei, periventricular nuclei, raphe nuclei, pontine area and medulla oblongata. It is concluded that there is a heterogeneous monoaminergic input to the lateral septal area organized in a complicated pattern along the longitudinal axis of the lateral septum.