Final answer:
Substance P functions as a neurotransmitter and neuromodulator in the gate control theory of pain, influencing pain perception by acting on the NK1 receptor in pain pathways.
Step-by-step explanation:
In gate control theory, substance P acts as a neurotransmitter and a neuromodulator in pain processing pathways within the spinal cord. Substance P is part of the tachykinin peptide family and is known to be the preferred endogenous ligand for the neurokinin 1 (NK1) receptor. Through its action at the NK1 receptor, substance P plays a significant role in conveying pain signals to the central nervous system, thereby influencing our perception of pain. Notably, substance P metabolites also have an impact on the modulation of nociceptive (pain) information and potentially have implications in the development of new analgesic drugs.