Substance P is found in which type of primary afferent nerve fibers?

Explore the Biological Bases of Behavior Test. Prepare with engaging flashcards and multiple choice questions, each featuring explanations. Start practicing today!

Substance P is a neuropeptide released by small-diameter, unmyelinated primary afferent neurons that carry nociceptive (pain) signals. These are the C fibers, which convey dull, slow, throbbing pain and contribute to inflammatory pain responses in the dorsal horn and peripheral tissue. Because C fibers are peptidergic and able to release substances like Substance P, this neuropeptide is characteristically found there. In contrast, A-delta fibers are fast, myelinated nociceptors that primarily use glutamate as a transmitter for sharp pain, A-beta fibers carry non-nociceptive touch, and B fibers are autonomic and not involved in somatic pain transmission.