Lengthwise view of the rat brain showing the distribution of opioid peptide–producing neurons. The opioid peptides—endorphins (teal), enkephalins (purple), and dynorphins (blue)—and the neurotransmitter dopamine are involved in the processes of reward and reinforcement. Endorphin-producing neurons are located primarily in the arcuate nucleus (ArcN) of the hypothalamus and the nucleus tractus solitarius (NTS); they extend to and release endorphin in various brain areas (purple). Nerve cells in several regions produce enkephalins and dynorphins, which may be released either in the same region or in distant regions through networks of neurons (not shown). The mesolimbic dopamine system (orange line) is influenced by the actions of endogenous opioids and carries dopamine from the ventral tegmental area (VTA) to various parts of the brain.

NOTE: Amyg = amygdala; CPu = caudate putamen; FC = frontal cortex; Hpc = hippocampus; NAc = nucleus accumbens; PaG = periaqueductal gray area; Sept = septum.

SOURCE: Gianoulakis, C. Alcohol-seeking behavior: The roles of the hypothalamic-pituitary-adrenal axis and the endogenous opioid system. Alcohol Health & Research World 22(3):202–210, 1998. PMID: 15706797

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Updated: October 2009