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Reproductive Experience Increases Prolactin Responsiveness in the Medial Preoptic Area and Arcuate Nucleus of Female Rats

Centre for Neuroendocrinology and Department of Anatomy and Structural Biology (G.M.A., D.R.G., W.v.d.A.), University of Otago School of Medical Sciences, Dunedin 9054, New Zealand; and Department of Biomedical Sciences (R.S.B.), Tufts Cummings School of Veterinary Medicine, North Grafton, Massachusetts 01536

Address all correspondence and requests for reprints to: Dr. Greg Anderson, Centre for Neuroendocrinology and Department of Anatomy and Structural Biology, University of Otago School of Medical Sciences, P.O. Box 913, Dunedin, New Zealand. E-mail: greg.anderson{at}anatomy.otago.ac.nz.

The experience of pregnancy plus lactation produces long-term enhancements in maternal behavior as well as reduced secretion of prolactin, a key hormone for the initial establishment of maternal care. Given that prolactin acts centrally to induce maternal care as well as regulate its own secretion, we tested whether prolactin receptors in brain regions known to regulate behavioral and neuroendocrine processes were up-regulated and more responsive to prolactin in reproductively experienced females. Diestrous primiparous (8 wk after weaning) and age-matched virgin rats were treated with 250 µg ovine prolactin sc or vehicle and the brains collected 2 h later for measurement of mRNA for genes involved in prolactin signaling. Reproductively experienced rats had lower serum prolactin concentrations, compared with virgin rats, suggesting enhanced prolactin feedback on the arcuate neurons regulating prolactin secretion. In the medial preoptic area and arcuate nucleus (regions involved in regulating maternal behavior and prolactin secretion, respectively), the level of long-form prolactin receptor mRNA was higher in primiparous rats, and prolactin treatment induced a further increase in receptor expression in these animals. In the same regions, suppressors of cytokine signaling-1 and -3 mRNA levels were also markedly increased after prolactin treatment in reproductively experienced but not virgin rats. These results support the idea that reproductive experience increases central prolactin responsiveness. The induction of prolactin receptors and enhanced prolactin responsiveness as a result of pregnancy and lactation may help account for the retention of maternal behavior and shifts in prolactin secretion in reproductively experienced females.

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				G. M. Anderson, D. C. Kieser, F. J. Steyn, and D. R. Grattan Hypothalamic Prolactin Receptor Messenger Ribonucleic Acid Levels, Prolactin Signaling, and Hyperprolactinemic Inhibition of Pulsatile Luteinizing Hormone Secretion Are Dependent on Estradiol Endocrinology, April 1, 2008; 149(4): 1562 - 1570. [Abstract] [Full Text] [PDF]