Regulation of prolactin receptor expression by estradiol in the female rat brain

Prolactin (PRL) receptors have been identified in many tissues, including the brain, but little is known about their distribution and regulation. In the female rat brain, ovariectomy significantly (p < 0.05) decreased PRL binding capacity, but not the affinity, in the hypothalamus and pons-medulla. Using reverse transcription and polymerase chain reaction (RT-PCR) amplification and Western blot analyses we found both the long and short forms of the PRL receptor mRNAs and proteins in the hypothalamus, pons-medulla and cortex in the female rat. Ovariectomy decreased the expression of short, but not the long form of the PRL receptor in the hypothalamus and pons-medulla, but not the cortex. Administration of estradiol (1.0 mg per 100 g b.w.) restored the PRL binding capacity, protein and mRNA levels of the short form of the receptor back to control levels. These results suggest that the expression and distribution of PRL receptors in the brain are differentially regulated in specific brain regions.