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either of two pentapeptides, composed of four identical amino acids and either leucine or methionine, referred to as leu-enkephalin and met-enkephalin. The enkephalins function as neurotransmitters or neuromodulators at many locations in the brain and spinal cord and are involved with pain perception, movement, mood, behavior, and neuroendocrine regulation; they are also found in nerve plexuses and exocrine glands of the gastrointestinal tract.
enkephalin/en·keph·a·lin/ (en-kef´ah-lin) either of two pentapeptides (leu-enkephalin and met-enkephalin) occurring in the brain and spinal cord and also in the gastrointestinal tract; they have potent opiate-like effects and probably serve as neurotransmitters.
Either of two closely related pentapeptides having opiate qualities and occurring in the brain, spinal cord, and other parts of the body.
Etymology: Gk, enkepalos, brain, in, within
one of two pain-relieving pentapeptides produced in the body, located in the pituitary gland, brain, and GI tract. Axon terminals that release enkephalins are concentrated in the posterior horn of the gray matter of the spinal cord, in the central part of the thalamus, and in the amygdala of the limbic system of the cerebrum. Enkephalins function as neurotransmitters or neuromodulators and inhibit neurotransmitters in the pathway for pain perception, thereby reducing the emotional as well as the physical impact of pain. Methionine-enkephalin and isoleucine-enkephalin are each composed of five amino acids, four of which are identical in both compounds. These two neuropeptides can depress neurons throughout the central nervous system. Although it is not known exactly how these neuropeptides function, the enkephalins are natural pain killers and may be involved, with other neuropeptides, in the development of psychopathological behavior in some cases. Compare endorphin.
either of two naturally occurring pentapeptides (methionine enkephalin and leucine enkephalin) isolated from the brain, which have potent opiate-like effects and probably serve as neurotransmitters. They are classified as endorphins.