This is the 2007 version. Click here for the 2017 chapter 02 table of contents.

Brain Peptides

The first chemicals identified as transmitters were relatively simple substances. All except acetylcholine consisted of a single amino acid or its derivatives. Beginning in the mid-1970s, researchers began to suspect many other substances were transmitters. Most were peptides—strings of amino acids. Once scientists began looking at peptides as potential transmitters, they kept finding more.

What does substance P do, among other things? Is it rare or common, in brain tissue?

The first neuropeptide to be discovered was a sequence of 12 amino acids called substance P. It is a transmitter of pain signals. Substance P was discovered by accident in 1931 when researchers were trying to isolate a different compound. Two researchers at Brandeis University pinpointed its chemical structure in 1970. Substance P was found in virtually all brain tissue and inspired much research.

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