Do fish use chemicals in pain transmission?

Substance P is widely distributed in the brain, spinal cord, and peripheral nervous system in people. It is an important element in pain perception, and in the transmission of pain information into the central nervous system.

Canandian scientist found the distribution of a P-like substance in the brain of brown ghost knifefish.

Substance P-Like Immunoreactivity in the Brain of the Gymnotiform Fish Apteronotus leptorhynchus: Presence of Sex Differences, Weld, M and Maler, L, Journal of Chemical Neuroanatomy, Vol. 5:107-129, 1992, University of Ottawa

Fish Pain