Sugar, Suckling Trigger Natural Pain Control

13 Mar 2013 --- People come equipped with built-in pain control mechanisms. The tricky part is switching them on. Neuroscientists at the University of Maryland at Baltimore have found that sugar and suckling activate natural pain-modulating systems in babies.

They also learned that this mechanism is controlled at least partly in the spinal cord. Although their research was conducted on a rat model, the findings could lead to new ways to stimulate natural pain-control mechanisms in human infants following injury and inflammation. Dr. Ronald Dubner, Dr. Ke Ren and colleagues report on a study of the underlying mechanisms, spinal cord involvement and developmental implications of the power of sugar water and suckling to reduce sensitivity to pain, in the February 18, 1997 issue of The Proceedings of the National Academy of Sciences. Dubner is chairman of oral and craniofacial biological sciences at the University of Maryland Dental School, where Ren is an assistant professor. "Pain is a serious clinical problem in premature, newborn and young infants," Dubner said. "Fear that anesthetic agents produce respiratory depression and low blood pressure often result in insufficient pain control. These studies will lead to a better understanding of the development of analgesic mechanisms and provide new clinical approaches for engaging endogenous analgesic mechanisms in premature, newborn and young infants."

Dubner, Ren and colleagues evaluated the effectiveness of sugar water and suckling on responses to heat and pressure of 10-day-old rats with inflamed forepaws. They found that five to 10 minutes of suckling combined with three minutes of sugar water given by mouth doubled the baby rats’ forepaw tolerance to pain. The suckling-sugar treatment did not reduce hindpaw sensitivity to the same stimuli.

Study results suggest that the parts of the central nervous system controlling upper and lower extremities mature at different rates, Dubner said. This information could be vital to the development of effective clinical pain-control for infants.

The neuroscientists also measured the expression of a protein called Fos, which is produced by neurons firing in response to painful stimuli. They found that the suckling and sugar treatment significantly reduced the amount of Fos in the upper spinal column, where the response to forepaw inflammation and pain is controlled. Fos expression in the lower spine after hindpaw inflammation did not drop significantly.

Very little has been known about where the neurons for pain sensitivity are located. This outcome indicates that the mechanism for the reduced sensitivity to pain that results from suckling and sugar resides at least in part in the spinal column, Dubner said. "These studies suggest that there is an interaction between the nerves that transmit perception of taste and touch in the mouth and pain-modulating circuits in the brain," he said. "Future studies will need to analyze the contribution of each component, including feeding sucrose, non-nutritive suckling and maternal contact."

The research was supported by National Institutes of Health grants and a Research Scientist Award.