By Charlotte King
New insights into the neurones that influence milk production, obesity and sex drive, may help develop more targeted treatments with fewer side effects for conditions affecting these processes.
The hormone prolactin, normally associated with triggering breast milk production, is regulated due to “rhythmic oscillations” in a group of brain cells according to researchers at the Karolinska Institute in Sweden.
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Prolactin is normally suppressed in males and in non-pregnant females by another hormone, dopamine, which is released every 20 seconds by a group of brain cells called the TIDAs. The team at the Institute studied the electrical activity in this group of brain cells in rats and found a robust 0.05Hz oscillation. The release of dopamine means that normally people do not produce breast milk and have a regular metabolism and libido. So abnormal firing of the TIDAs could potentially cause abnormal prolactin levels.
According to David Lyons who worked on the research at the Karolinska Institute, there are “all manner of reasons” why there might be an increase in prolactin, as the brain is a complex network of feedback loops and “disturbed modulation of the group of neurones can cause problems”. These reasons could include brain adenomas which are normally benign tumours that can eventually turn malignant.
Also certain drugs, notably those for psychological conditions such as schizophrenia and bipolar disorder, affect the production of prolactin by blocking the dopamine receptors. As dopamine normally inhibits prolactin, prolactin is released abnormally, meaning psychiatric patients using these drugs could now also be lactating.
Currently the drug bromocriptine is used to regulate prolactin. It mimics dopamine, so adding it decreases the release of prolactin. But, according to Dr Lyons, because the drug is not delivered in a targeted way to the prolactin pathway, there are side effects, one of which affects the reward and addiction pathways in the brain.
The more scientists understand about the neurones that regulate prolactin, the more potential there is to treat conditions caused by its abnormal levels, with fewer side effects for patients.
David Lyons says that “by understanding how the oscillation of these TIDA neurones works, and whether other prolactin inhibitory or release factors modulate the rhythms, we have a greater chance of producing therapies that can target these neurones specifically.”
Jonathan Fry who works on hormones and the nervous system at University College London agrees. “The findings open up new possibilities for manipulating the release of prolactin. However, before taking this idea much further, the investigation must be extended to mature animals.”