Peptides with transmitter-like characteristics are found in many areas of the brain, and may cause inhibition, excitation or both when applied to target neurons. These peptides are synthesized as secretory products and grouped into families according structural and functional similarity. Substance P, a member of the tachykinin family, is thought to play a role in nociceptive transmission in the dorsal horn of the spinal cord. Its proposed role is based on a number of anatomical and physiological findings. For example, substance P is present in high concentration in a subpopulation of fine-diameter primary sensory axons and in nerve terminals in dorsal horn regions where primary sensory nociceptors terminate. It specifically excites nociceptive dorsal horn and is released in the spinal cord in vivo during activation of nociceptive primary sensory fibers. Additionally, substance P receptor antagonists have been shown to block nociceptive responses in vivo and in vivo.
NC1/34 is specific for substance P. It reacts with mammalian substance P and has been shown to also cross-react with a substance P-like protein in the pigeon brain. It binds to subpopulations of nerve terminals and cell bodies in the central nervous system. The initial characterization of the antibody was in rat brain. The antibody does not cross-react with other mammalian brain peptides tested including [Leu]enkephalin, [Met]enkephalin, somatostatin, or β-endorphin. NC1/34 recognizes an epitope in the carboxy terminal region of substance P and thus does not differentiate substance P from neurokinins A and B. Substance P conjugated to carrier protein was used as immunogen.