Androgen regulation of an antigen expressed in regions of developing brainstem monoaminergic cell groups

To examine the regulation of brain development by gonadal steroids we are using monoclonal antibodies obtained with neonatal rat brain homogenates as immunogens. One antibody, 3D10, binds selectively in regions of identified monoaminergic neuronal cell groups in the brainstem. Characterization of 3D10 immunoreactivity was carried out using free-floating 50 microns tissue sections from perinatal rats. The strongest reactivity was seen on postnatal day 1 in the locus coeruleus (A6) and in the regions of the A4 (dorsal) and A5 (ventral) noradrenergic cell groups. Immunoreactivity was also seen in the raphe magnus, pallidus and obscuris. Faint immunoreactivity was seen in the more rostral and median raphe nuclei and in the midbrain dopaminergic cell groups of the ventral tegmentum and substantia nigra. The number of 3D10 immunoreactive cells in all groups was greatest perinatally and decreased with age. The number of immunoreactive cells in the A4 region of males decreased at an earlier age than in females. Female offspring treated prenatally with testosterone propionate also had fewer immunoreactive cells in the A4 region at earlier ages, approximating the time course in the male. Thus, changes in the number of 3D10 immunoreactive cells reveal hormonal control of the time course of a developmental process in a selective population of neurons.