TRUSTEES OF TUFTS COLLEGE INC
The hormone prolactin (PRL) in combination with the steroidal and neuropeptidergic changes accompanying pregnancy stimulate the onset of maternal care. The actions of PRL have been clearly demonstrated in studies in the rat. Direct infusions of PRL into the medial preoptic area (MPOA) of steroid-treated, inexperienced nulliparous female rats stimulate a rapid onset of maternal care towards foster young, whereas infusions of a PRL receptor antagonist into this same region delay the onset of maternal behavior. Moreover, deletion of the PRL receptor gene in mice produces deficits in maternal behavior. The primary source of PRL involved in stimulating maternal behavior appears to be the pituitary gland. However, the rat placenta also produces a lactogenic hormone, placental lactogen, which binds to the PRL receptor, gains access to the cerebrospinal fluid, and can stimulate the onset of maternal behavior. Whereas the predominant sources of lactogenic hormones therefore are found in peripheral endocrine tissues, there have been re0orts, although equivocal, that the brain itself produces PRL. These later reports provide support for the hypothesis that a centrally derived PRL may be involved in the transition from maternal care being regulated by a peripheral PRL input to a central PRL control. Other recent research also supports the idea that a shift in lactogenic regulation of maternal care occurs following prior maternal care. Specifically, the central PRL receptor system becomes more sensitive to PRL as a function of the female rat having prior parental experience. The objective of this supplemental request is to use molecular biological techniques, i.e. Taqman ® to access whether and to what extent the PRL gene is expressed in the maternal brain. In addition, examination of the regulatory control of the neural PRL gene will be conducted. These are important research objectives which are central to the initial grant hypothesis. They will address a controversial issue as to whether indeed there is a central source of PRL. Supplemental resources will be used to hire additional personnel to address these objectives.