ATLAS OF THE NEURONS THAT EXPRESS MESSENGER-RNA FOR THE LONG FORM OF THE PROLACTIN RECEPTOR IN THE FOREBRAIN OF THE FEMALE RAT

Prolactin has a variety of important physiological effects on peripher al tissue and on the brain. The behavioral effects of prolactin includ e the induction of maternal behavior and increased food intake. Prolac tin acts via its cognate receptors which have two forms, a short and a long for m. The long form of the receptor is predominant in the preop tic area-hypothalamus and is positioned to support maternal behavior s ince this form is regulated across pregnancy and lactation (Nagano and Kelly [1994] J. Biol. Chem. 269:13337-13345; Sugiyama et al. [1994] J . Endocrinol. 141:325-333). By using in situ hybridization with [P-33] labelled cRNA probe specific for the long form of the receptor mRNA(L -PRL mRNA) we have mapped, in brains from 2-and 21-day-old pregnant fe males, the neuroanatomical distribution of neurons expressing the long form of the receptor. Many neurons with high expression of L-PRL mRNA were located in the anteroventral periventricular nucleus, the medial preoptic area (MPO), specific subdivisions of the paraventricular and supraoptic nuclei, and in the arcuate and ventromedial nuclei. Labell ed neurons were also found in limbic system structures such as the bed nucleus of stria terminalis (BST) and the medial nucleus of the amygd ala, in a few thalamic nuclei, and in the central gray. All cells thro ughout the choroid plexus expressed high levels of L-PRL mRNA. The lev els of L-PRL mRNA were higher in females on day 21 of pregnancy in the MPO and in the choroid plexus, than in females on day 2 of pregnancy; levels in the ventromedial nucleus of the hypothalamus (VMH) were unc hanged across pregnancy. The neuroanatomical distribution of neurons e xpressing L-PRL mRNA may have special relevance for the mediation of m aternal behavior, lactation, sexual behavior, and feeding. (C) 1997 Wi ley-Liss, Inc.