Origin of the dopaminergic innervation of the rat dorsal raphe nucleus.

The aim of the present study was to describe the distribution of dopamine (DA) fibres in the dorsal raphe nucleus (DRN) and to determine their neurones of origin. Using an anti-DA antibody, we observed a moderate density of DA varicose fibres over the DRN and a dense plexus of DA fibres in the ventrolateral central grey. With a sensitive retrograde tracing technique combining the use of cholera toxin subunit b with tyrosine hydroxylase immunohistochemistry, after tracer injections in the DRN, a few double-labelled cells were observed in the ventral tegmental area and the A10 dorsocaudal DA cell group, as already described. In addition, a moderate number of double-labelled cells was seen in the A11 hypothalamic DA cell group.