the greatest relative increases in opiate receptor density were observed in the nucleus accumbens , the amygdala , striatal patches , nuclei of the thalamus and hypothalamus , layers i and iii of neocortex , substantia nigra compacta , midbrain periaqueductal gray regions , and the parabrachial nuclei of the brainstem .
C0025462
midbrain
C0006121
the