Am J Psychiatry 1978; 135:645-652
Copyright © 1978 by American Psychiatric Association
The opiate receptor and morphine-like peptides in the brain
SH Snyder
Opiate receptors--neuronal membrane proteins that have been identified by
the direct binding to membranes of radioactive opiates--have been shown to
mediate the pharmacological effects of opiate drugs. Examination of brain
extracts for substances that mimic effects of opiates on the opiate
receptor permitted identification of the enkephalins, two peptides, each
containing five amino acids, which are the normal substrates for the opiate
receptor. Enkephalins are contained in specific neurons localized to areas
of the brain enriched in opiate receptors. Enkephalin-containing neurons
and opiate receptors are concentrated in portions of the brain that mediate
pain perception, emotional behavior, and other functions altered by
opiates. beta- Endorphin, an opiate-like peptide containing 31 amino acids,
is localized to the pituitary gland from which it can be released into the
circulation to act presumably at peripheral target organs. In the brain
beta-endorphin is concentrated in the hypothalamus.
