Newswise — In the October 2006 issue of the journal Endocrinology, a collaborative research study by scientists at Cummings School of Veterinary Medicine at Tufts University and the University of Otago Medical School in Dunedin, New Zealand, shows that pregnancy and lactation in rodents produce long-term changes in hormone receptor actions in a mother's brain that may affect maternal behavior as well as her response to stress.

"It appears that hormonal changes occurring in rats after they nurse their pups may bring about endocrine and neuroendocrine changes that help produce better mothering skills with each pregnancy and reduce the mother's anxiety levels as she matures," said Robert S. Bridges, PhD, the senior author of this paper and head of the reproductive biology section at Tufts' Cummings School of Veterinary Medicine.

In this study, female rats that had undergone a single pregnancy and nursed their offspring displayed higher levels of prolactin hormone receptor activity in the brain, as well as a greater receptor response when treated with prolactin weeks following the last contact with their young. Prolactin is produced by the pituitary gland and plays an established role in a range of reproductive functions, including milk production.

The present study is the first to demonstrate long-term changes in the prolactin neural system, a system that Bridges' research group previously identified as crucial for stimulating the establishment of maternal behavior. In addition, since prolactin is known to reduce the stress response of nursing mothers, the implication of the present findings is that prior reproductive experience may reduce the female's response to stress well beyond weaning.

"These new findings indicate that the maternal brain is a dynamic and changing structure, and suggest that increased activity of the prolactin receptor system in females who have given birth and breast fed their offspring may help mothers improve their abilities to both nurture children and manage stress," Bridges added. "This possibility warrants further investigation as to how reproductive experience alters the mother's physiology and behavior."

Greg M. Anderson, David R. Grattan, Willemijn van den Ancker, Robert S. Bridges. Endocrinology, October 2006, 147 (10):4688-4694 "Reproductive Experience Increases Prolactin Responsiveness in the Medial Preoptic Area and Arcuate Nucleus of Female Rats."

Founded in 1978 in North Grafton, Mass., Cummings School of Veterinary Medicine at Tufts University is internationally esteemed for academic programs that impact society and the practice of veterinary medicine; three hospitals that treat more than 28,000 animals each year; and groundbreaking research that benefits animal, human, and environmental health. Tufts University was the first institution of higher education to offer a four-year, combined doctor of veterinary medicine (D.V.M.) and master of public health (M.P.H.) degree program. In 2004, Tufts launched two combined doctor of veterinary medicine and master of science (D.V.M./M.S.) degree programs to prepare students for careers in biomedical research.

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Endocrinology (Oct. 2006, 147 (10):4688-4694 "Reproductive Experience Increases Prolactin Resopnsiveness in the Medial Preoptic Area and Arcuate Nucleus of Female Rats" (Vol. 147, Iss. 10, Oct-2006)