Neuroscientists at the University of Southern California have identified a chemical that can carry the electrical signal that alerts the brain to low blood sugar levels.
The key to the new finding, which is expected to yield new insights in the fight against diabetes, is the neurotransmitter norepinephrine.
According to the researchers, the chemical travels from the hindbrain, which receives warnings of low glucose levels from the body, to the paraventricular hypothalamus, which authorises the consumption of energy stores to replace the missing sugars.
"There's a huge interest in how the body senses glucose," said Alan Watts, director of the Neuroscience Research Institute at USC and a co-author of the study, which has been published in the Journal of Neuroscience.
"How that information is processed by the brain is really a hot current topic," he added.
Arshad Khan, a research assistant professor at the university, says that knowing how neurons relay hypoglycemia warnings is critical to understanding the overall glucose sensing mechanism in the brain.
"That's why I'm interested in this system, because it's very poorly understood," Khan said.
"If we don't know how an automobile's fuel system works to begin with, then how can we expect to fix one when it is not burning fuel appropriately," he added.
During the study, a group of animals were injected with insulin to drop their blood sugar levels, while another group was injected with norepinephrine directly into the paraventricular nucleus.
The researchers then compared brain tissue sections from both groups of animals, and examined their blood samples for the presence of hormones released by paraventricular nucleus activity.
The same paraventricular neurons lit up in both sets of animals, and the animals displayed similar increases in hormone levels, suggesting that norepinephrine plays a role in transmitting the hypoglycemia warning.
"Norepinephrine is capable of activating these signals just like hypoglycemia does," Khan said.
He insists that norepinephrine is not only sufficient but necessary for conveying hypoglycemia signals from the hindbrain.