enkephalin immunoreactivity was detected in many groups of nerve cell bodies , fibers and terminals in the limbic system , basal ganglia , hypothalamus , thalamus , brain stem and spinal cord . beta-endorphin and acth immunoreactivity was limited to a single group of nerve cell bodies in and around the arcuate nucleus and in fibers and terminals in the midline areas of the hypothalamus , thalamus and mesencephalic periaqueductal gray with lateral extensions to the amygdaloid area .
C0006121
brain stem
C0025462
mesencephalic