Estrogen effects on tyrosine hydroxylase-immunoreactive cells in the ventral mesencephalon of the female rat: further evidence for the two cell hypothesis of dopamime function

The present study was undertaken to examine the differential effect of estr ogen (E) on the expression of tyrosine hydroxylase (TH) in the substantia n igra compacta (SNc) and in two subdivisions of the ventral tegmental area i n ovariectomized (ovx) and ovx plus estradiol benzoate (ovx + E)-treated fe male rats. Cell counting of TH-immunoreactive perikarya of the SNc, paranig ral (PN) and interfascicular (TF) nucleus was performed and compared. Our f indings demonstrate that E eliminated TH immunoreactivity from a number of midbrain neurons, while it seemingly did not affect it in others. This sign ifies a differential effect of E on ventral mesencephalic dopaminergic neur ons. (C) 2000 Elsevier Science B.V. All rights reserved.