Peptides as neuromodulators in primary sensory neurons.

The neurokinins, in particular substance P, can be taken as prototypes of modulating peptides in primary sensory neurons. They are transported to and liberated from both the central and peripheral ends of sensory neurons. At the CNS level, they facilitate nociceptive signals while at the periphery, they are released antidromically. The antidromically-released neurokinins act synaptically and non-synaptically in autonomic ganglia and other peripheral targets.