“While sociability is definitely a primary need of developing mammals, it isn’t a static need,” Dietrich explained. In their work, researchers measured Agrp activity in mice at different ages, from weanlings through adulthood. In a series of experiments, the researchers measured Agrp activity after socially isolating mice and then after reuniting them with other mice. They found that social isolation strongly activates Agrp neurons in juveniles, and that social reunions bring their activity back to low levels. “They’re not signaled to Agrp neurons.