Summary:
A new discovery offers new insight into regulation of water and food intake. Neuroscientists recorded neuronal activity in real-time in awake mice when presented with food or water and identified anticipatory changes in neuronal activity in the seconds prior to drinking.
Using leading-edge technology, neuroscientists at Beth Israel Deaconess Medical Center (BIDMC) gained new insight into the brain circuit that regulates water and food intake. In a new study, the team of researches monitored the activity of neurons that secrete a hormone in response to ingesting food and water.
In their paper, published online today in Neuron, Researches demonstrated that a subset of neurons starts to prepare the body for an influx of water in seconds before drinking begins. These neurons help regulate intake by anticipating the effects of drinking from the ‘top down’ rather than taking cues from the body.
The study states that when we encounter sudden availability of food or water, our body starts to prepare itself for the upcoming bout of eating or drinking and predicts the deficits overall. This could lead to overshoots in eating or drinking with many negative consequences, said co-corresponding author, Mark Andermann, PhD, Assistant Professor of Medicine in the Division of Endocrinology, Diabetes and Metabolism at BIDMC.
Recording neuronal response to food and drink:
Andermann and colleagues, including co-corresponding author, Bradford B. Lowell, MD, PhD, a Professor of Medicine in the Division of Endocrinology, Diabetes and Metabolism at BIDMC, recorded the activity of neurons responsible for releasing the anti-diuretic hormone vasopressin in mice. Vasopressin plays a crucial role regulating the body’s relative concentration of water versus salt after eating or drinking, which could otherwise dramatically alter the mix. It is crucial that body has ways to prevent water concentration outside of cells from changing. Anticipating future consequences helps the body in maintaining balance.
In their experiments, Andermann and Lowell watched as the activity of vasopressin-releasing neuron rapidly decreased — within seconds — when water was presented to water-restricted rodents, before they even drank it. In contrast, the sight and smell of food increased the activity in these neurons — again, within seconds — but only following food consumption. That difference in timing suggested that separate neural networks regulate these reactions to water and to food.
This type of regulation was not known to exist and was discovered only last year. It occurs for all forms of homeostatic control. This could be implemented in regulating meal size without interfering with baseline appetite or with the pleasure of taking the first bite of something delicious.