REGULATION OF PROLACTIN RECEPTOR EXPRESSION BY ESTRADIOL IN THE FEMALE RAT-BRAIN

PROLACTIN (PRL) receptors have been identified in many tissues, includ ing the brain, but little is known about their distribution and regula tion. In the female rat brain, ovariectomy significantly (p < 0.05) de creased PRL binding capacity, but not the affinity, in the hypothalamu s and pons-medulla. Using reverse transcription and polymerase chain r eaction (RT-PCR) amplification and Western blot analyses we found both the long and short forms of the PRL receptor mRNAs and proteins in th e hypothalamus, pons-medulla and cortex in the female rat. Ovariectomy decreased the expression of short, but not the long form of the PRL r eceptor in the hypothalamus and pons-medulla, but not the cortex. Admi nistration of estradiol (1.0 mg per 100 g b.w.) restored the PRL bindi ng 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 regulat ed in specific brain regions.