There also are good economic and maternal health reasons that would seem to make a compelling case for breastfeeding for the six-to-12 months recommended by the American Academy of Pediatrics.
"However one major reason why women stop breastfeeding is low weight gain and growth rate of their baby," Steven L. Bealer of the University of Utah points out. His team of researchers decided to find out what factors might cause low weight gain.
They studied how blocking the oxytocin (OT) hormonal system, which serves several functions in the birth process and milk delivery during nursing (lactation), would affect offspring during and after birth. They found that if the central OT receptors in the pregnant females' brain are blocked during pregnancy, then their offspring's growth was reduced from the third day after birth through the two-week experiment.
Interestingly, the actual delivery itself wasn't affected nor was the number of "pups" in each litter. Even the delivery weights of the test females' offspring was the same as "control dams" pups' delivery weights.
A blocked OT system reduces post-natal weight gains
However what they did find was that in the mothers with blocked OT systems, the initial release of OT following the onset of pups suckling was significantly delayed compared to untreated females. "Finally, litter weight gain during a three-hour suckling period was significantly smaller in pups nursing dams that were treated with OT receptor blocker during gestation," Bealer reports.
"What we learned is that OT receptor stimulation during gestation is necessary for normal OT responsiveness and consequently for normal pup development during lactation," Bealer notes. "More efficient and longer lasting breastfeeding results in better human health throughout life," he adds, "so if the efficiency of the oxytocin system can be improved, perhaps it will encourage mothers to lengthen how long they breast feed their children."
Bealer is presenting at the American Physiological Society's 2005 Conference, "Neurohypophyseal Hormones: From Genomics and Physiology to Disease," and the latest developments toward clinical applications, July 16-20 in Steamboat Springs, Colorado.
He also is participating in the symposium, "Central control lactation," chaired by Bill Armstrong of the University of Tennessee School of Medicine, and Glenn Hatton, University of California, Riverside.
"Central oxytocin receptor blockade during gestation alters oxytocin release and pup development during lactation." Steven L. Bealer, William R. Crowley, David L. Lipschitz, University of Utah. Funded by U.S. Public Health Service grants.
Arrangements for on-site interviews, or telephone interviews during the meeting, can be through APS from Mayer Resnick (cell: 301-332-4402; office 301-634-7209, or mresnick@the-aps.org).
Sponsorships. The American Physiological Society thanks the following sponsors for their generous support of the conference: Astellas Pharmaceuticals Inc., GlaxoSmithKline Pharmaceuticals, NIH/NIDDK, Wyeth Research and Olympus America Inc.
Three APS Journals call for papers. In conjunction with the conference, three American Journal of Physiology (AJP) editions – AJP-Regulatory, Integrative and Comparative Physiology, AJP-Endocrinology and Metabolism, and AJP-Renal Physiology – have called for related papers for publication. The deadline for all editions is October 1, 2005.
The American Physiological Society was founded in 1887 to foster basic and applied bioscience. The Bethesda, Maryland-based society has more than 10,000 members and publishes 14 peer-reviewed journals containing almost 4,000 articles annually.
APS provides a wide range of research, educational and career support and programming to further the contributions of physiology to understanding the mechanisms of diseased and healthy states. In May 2004, APS received the Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring (PAESMEM).