Androgen receptor in the rat brain--assays and properties

Area of Science:

• Neuroendocrinology
• Molecular Biology
• Developmental Neuroscience

Background:

• The presence and function of androgen receptors in the developing brain have been debated.
• Previous studies lacked definitive evidence for a distinct androgen receptor in specific brain regions.

Purpose of the Study:

• To definitively identify and characterize the androgen receptor in the developing rat brain.
• To determine the localization and binding affinities of the androgen receptor in key brain areas.

Main Methods:

• Sucrose density gradient centrifugation.
• Hydroxylapatite chromatography.
• Binding assays using radiolabeled ligands.

Main Results:

• A distinct androgen receptor was identified in the 24-day-old rat hypothalamus, amygdala, and preoptic region.
• The receptor showed high affinity for dihydrotestosterone and testosterone (Kd ~1 x 10^-9 M) and estradiol (Kd ~2 x 10^-8 M).
• No significant binding was observed for other estrogens, antiestrogens, or glucocorticoids, and the receptor was absent in the cortex.

Conclusions:

• This study provides clear evidence for a specific androgen receptor in critical regions of the developing rat brain.
• The receptor's binding profile, particularly its affinity for estradiol, may explain previous uncertainties regarding its identification.
• The characterized androgen receptor's properties are consistent with those found in other mammalian tissues.