Nociceptors use multiple neurotransmitters to drive pain.

Nociceptors are excitatory neurons that express a range of neuropeptides and have the essential role of detecting noxious mechanical, thermal and chemical stimuli. Ablating these neurons profoundly reduces responses to pain. Here we investigated how nociceptive information is transmitted by developing genetic approaches to suppress glutamate transmission and neuropeptide signaling, individually and in combination. Remarkably, many pain responses persisted in mice where either nociceptor glutamate or neuropeptide signaling was blocked. By contrast, mice lacking both glutamate and neuropeptide transmission in nociceptors displayed profound pain insensitivity closely matching the effects of cell ablation. Together our results establish a role for neuropeptides as bone fide pain transmitters and demonstrate redundancy in nociceptor signaling, resolving long-standing questions about how pain is communicated to the brain.