Region-specific changes of tyrosine hydroxylase-immunoreactivity by estrogen treatment in female rat hypothalamus.

ABSTRACT

The effect of 17 beta-estradiol (E2) treatment for 28 days on tyrosine hydroxylase-immunoreactive (TH-IR) neurons in the periventricular preoptic nucleus (PPN) and medial preoptic area (MPA) of ovariectomized (OVX) rats was examined by morphometric analysis. The number of TH-IR neurons in the PPN of the E2-treated group was smaller than that of the OVX group, whereas the opposite result was found in the MPA; the number of TH-IR neurons in the MPA of the E2-treated group was larger than that of the OVX group. Numerous TH-IR neurons were found in the ventromedial portion of the MPA of the E2-treated group. In both the OVX and E2-treated groups, TH-IR neurons contained many short processes up to 40 microns in length. E2 treatment caused a significant decrement of the number of neurons containing the processes in the range of 10-40 microns length in the PPN, however it caused a significant increment of the number of neurons containing the processes in the range of 5-10 microns length in the MPA. These results suggested that immunoreactivity of TH in the PPN and MPA neuron are affected by E2 treatment and that E2 might modulate the production of TH in a region-specific pattern within the hypothalamus of the female rat.