How aggression-promoting brain peptide works in fruit flies

In addition to communicating with neurotransmitters, the brain also uses small proteins called neuropeptides. Neuropeptides send signals between neurons, working similarly to neurotransmitters but with key differences like a greater size and an ability to travel far away from the neuron that produces them. Though their importance is widely recognized, the way neuropeptides move around the brain and influence neurons has remained poorly understood—until now.