In their experiments, the researchers engineered mice to produce a fluorescent protein only in orexin neurons. Thus, the researchers could isolate the neurons in brain slices from the mice and perform precise biochemical and electrophysiological studies to explore how glucose acted on those neurons. In particular, the researchers performed experiments in which they exposed the neurons to the subtle changes in glucose levels known to occur in daily cycles of hunger and eating.
Their experiments showed that glucose inhibits orexin neurons by acting on a class of potassium ion channels known as "tandem pore" channels, about which little was known.
The sugar we (or mice, anyway) consume appears to inhibit neurons responsible for keeping us awake. Fortunately (for me, at least), the effect of chocolate appears to supersede the effects of glucose. Otherwise, I'd never get any work done.
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Hmm, any idea what evolutionary purpose such behaviour could have?
It seems rather unhelpful for animals to be sleepy just after feeding - falling asleep at a dangerous and popular feeding spot is surely suicidal?
My first guess is that mammals are more efficient in storing extra calories as fat or glycogen if we are less active after eating. I just hope that employers don't take these research findings as a reason to abolish the lunch hour (or half-hour).