Orexin neurons are cells in the brain that produce the
signalling molecule orexin, which is linked to anxiety and stress.
Scientists at the Francis Crick Institute have discovered that
these cells are inactivated by eating.
They suggest that this may be a reason people eat more when they
feel anxious or stressed.
Furthermore inactivation of orexin neurons is linked to weight
gain - although this can be reversed by minor dieting.
Denis Burdakov of the Crick led the study, which was carried out
in mice. The mice were allowed to eat normally while the
researchers used fiber photometry, a technique for recording brain
cell activity, to see what happened to their orexin cells as they
ate.
The activity of these cells decreased within milliseconds of the
mice starting to eat and stayed lower the whole time they were
eating. This was irrespective of what the mice ate, and happened
even when they were eating liquid and calorie-free types of
food.
Lars Fugger's team at the Weatherall Institute of Molecular
Medicine at the University of Oxford created transgenic mice that
lacked orexin cells altogether. These mice overate and became
overweight - although the researchers found that this weight gain
was preventable by mild dieting.
This suggests that non-drug interventions may be useful for
managing weight gain associated with reduced orexin signalling - or
that eating (even calorie-free food) might be a way to head off
anxiety disorders in people with overactive orexin cells.
"Further research into neuroscience-based lifestyle
interventions for anxiety and obesity might lead to treatments that
are easier to implement and have fewer side effects," say the
scientists.
The paper, Inhibitory Interplay between Orexin Neurons and Eating, is
published in Current Biology.