DIFFERENTIAL EXPRESSION OF THE 2 FORMS OF PROLACTIN RECEPTOR MESSENGER-RNA WITHIN MICRODISSECTED HYPOTHALAMIC NUCLEI OF THE RAT

The prolactin receptor (PRL-R) has recently been identified in various hypothalamic nuclei of female rats. In this study, expression of both the short- and long-forms of PRL-R mRNA was investigated in 11 microd issected hypothalamic nuclei of ovariectomized, estrogen-treated rats. Specific nuclei were micropunched from 300-mu m thick frozen coronal sections with autoclaved stainless steel needles of 300 or 500 mu m di ameter. Total RNA was extracted from the punched tissue, and the two f orms of PRL-R mRNA were detected by reverse transcription polymerase c hain reaction (RT-PCR) using specific primers. The RT-PCR product was verified by Southern hybridization with a digoxigenin-labelled oligonu cleotide probe common to both forms. The results showed that both form s of PRL-R mRNA were expressed to varying degrees in the choroid plexu s, cerebral cortex and various hypothalamic nuclei, including: ventrom edial preoptic nucleus, ventrolateral preoptic nucleus, medial preopti c nucleus, suprachiasmatic nucleus, supraoptic nucleus, paraventricula r hypothalamic nucleus, periventricular hypothalamic nucleus, arcuate nucleus, ventromedial hypothalamic nucleus, and median eminence. Of th ese brain regions, the choroid plexus expressed the highest level whil e the suprachiasmatic nucleus contained the lowest level of mRNA. Ther e was no expression detected in the dorsomedial hypothalamic nucleus. The choroid plexus, supraoptic nucleus and paraventricular hypothalami c nucleus had higher levels of the short-form of the PRL-R mRNA than t he long-form, whilst other hypothalamic nuclei preferentially expresse d the long-form of the PRL-R mRNA. The differential expression of PRL- R gene suggests that the two forms may be differentially regulated in specific brain regions and may mediate different functions of PRL. (C) 1998 Elsevier Science B.V. All rights reserved.