PROLACTIN RECEPTOR MESSENGER-RNA LOCALIZATION IN THE HYPOTHALAMUS BY IN-SITU HYBRIDIZATION

Prolactin receptors may mediate the action of prolactin in the brain t o influence behavior and neuroendocrine secretions. We recently demons trated prolactin receptor gene expression in the anterior and medial b asal hypothalamus and not in the cortex by the reverse transcription-p olymerase chain reaction. In this paper, we localize the prolactin rec eptor gene expression to individual cells with in situ hybridization. Several steps in the in situ hybridization method were modified to inc rease sensitivity by using (i) probes complementary to the coding sequ ence of the extracellular binding domain common to both long and short prolactin receptor, (ii) more stringent hybridization and wash condit ions to reduce background and (iii) higher specific activity, more com plex and saturating amounts of probe. We detected prolactin receptor g ene expression in cells of the periventricular area of the preoptic nu cleus, medial preoptic nucleus, supraoptic nucleus, rostral arcuate nu cleus and choroid plexus. Cortical brain tissue, which has been demons trated previously by reverse-transcription polymerase chain reaction t o be lacking in prolactin receptor mRNA, did not have any detectable s ignal for the receptor mRNA and was used as an indication of backgroun d levels of signal. The mean area of silver grains over labeled cells in periventricular area of the preoptic nucleus, medial preoptic nucle us, supraoptic nucleus, arcuate nucleus, lateral ventromedial nucleus was at least 10 times greater than the background in the cortex of the same brain section.