Encoding of danger by parabrachial CGRP neurons.

Animals must respond to various threats to survive. Neurons that express calcitonin gene-related peptide in the parabrachial nucleus (CGRP neurons) relay sensory signals that contribute to satiation and pain-induced fear behaviour, but it is unclear how they encode these distinct processes. Here, by recording calcium transients in vivo from individual neurons in mice, we show that most CGRP neurons are activated by noxious cutaneous (shock, heat, itch) and visceral stimuli (lipopolysaccharide). The same neurons are inhibited during feeding, but become activated during satiation, consistent with evidence that CGRP neurons prevent overeating. CGRP neurons are also activated during consumption of novel foods or by an auditory cue that has previously been paired with electrical footshocks. Correspondingly, silencing of CGRP neurons attenuates the expression of food neophobia and conditioned fear responses. Therefore, in addition to transducing primary sensory danger signals, CGRP neurons promote affective-behavioural states that limit harm in response to potential threats.