When a mother is breast-feeding her child, her brain is performing some interesting background operations. A team of researchers from China, France, Italy, and the United Kingdom have modeled a process that shows how suckling leads to a buildup of oxytocin – the “trust” hormone – in the mother’s brain. Their study is published in the July 18 issue of the open-access journal PLoS Computational Biology.

Oxytocin is a hormone that recently has become associated with trust and love in humans and other mammals. The hormone is released in large amounts during labor (when the cervix and vagina are distended). When it enters the bloodstream, it is responsible for milk to be released from the mammary gland. Research has also shown that oxytocin in the brain is associated with a strengthening of the mother-child bond. The effects of oxytocin, however, are driven by a large amount of the hormone that is abruptly released and spread throughout the brain. Existing research on oxytocin has been unable to modify the behavior of individual neurons in order to elicit the large, regular pulses of the hormone.

Prof. Jianfeng Feng, co-author of the study, said, “For thirty years we have known that these pulses arise because, during suckling, oxytocin neurons fire together in dramatic synchronized bursts, but exactly how these bursts come about has puzzled us so far.” However, this latest research by a group of experimental and theoretical neuroscientists has led to a breakthrough in understanding oxytocin.

The researchers were able to demonstrate that during suckling, oxytocin cells being releasing the hormone not only from their nerve endings, but also from their dendrites – part of the neuron that is usually associated with receiving information, not transmitting it. Dendrites usually construct a weak neural network, but the scientists have determined that oxytocin coming from the dendrites enhances the communication between neurons and begins a positive-feedback process on activity. This ultimately leads to and manages the observed “swarm” of oxytocin – massively intense and recurring bursts of release.

“Many neurons make peptides that act as messengers within the brain, and many of these are also released from dendrites, so this model may reflect a common pattern-generating mechanism in the brain,” conclude the authors.

Emergent Synchronous Bursting of Oxytocin Neuronal Network
Rossoni E, Feng J, Tirozzi B, Brown D, Leng G, et al.
PLoS Computational Biology (2008). 4(7):e1000123.
doi:10.1371/journal.pcbi.1000123
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Written by: Peter M Crosta