Comparative topography of dopamine- and tyrosine hydroxylase-immunoreactive neurons in the rat arcuate nucleus.

The distribution of dopamine (DA)-immunoreactive (IR) cells is described in the rat arcuate nucleus of the hypothalamus and its adjacent areas and compared with that of tyrosine hydroxylase (TH)-IR cells. Small DA-IR cells were seen to be aggregated mainly in the dorsomedial part of the nucleus, but were hardly detectable in its ventrolateral portion and neighbouring periarcuate region which showed many larger TH-IR cells. This study reveals, for the first time, the differences in the respective topography of those neurons which actually contain detectable DA and those which contain TH, the initial synthesizing enzyme of catecholamine.