What neuropeptide acts as a neurotransmitter and is concentrated in the dorsal horn of the spinal cord?

Substance P is the neuropeptide that acts as a neurotransmitter and is particularly concentrated in the dorsal horn of the spinal cord. This region is central to processing pain and nociceptive signals. Substance P plays a key role in transmitting pain information from peripheral neurons to the central nervous system. It is released from the terminals of nociceptive (pain-sensing) neurons and binds to neurokinin-1 receptors on postsynaptic neurons, which facilitates the perception of pain.

In the context of pain processing, Substance P contributes to the inflammatory response and is involved in the modulation of pain signals. Its presence in the dorsal horn highlights its important role in the complex mechanisms of pain signaling and perception. The other options, while significant neurotransmitters or modulators in the nervous system, do not have the same specific association with pain transmission or concentration in the dorsal horn as Substance P does.