Fig. (5) β-endorphin observed in the lateral PAG.Photographs show β-endorphin observed in the lateral PAG. Each photograph represents a square of 100 Ã— 100 µm. A: control (group 1), B:
formalin-injected (group 2), C: electrically stimulated to the CeA (group 3), D: sham-operated (group 4). β-endorphin in the lateral PAG was
increased by noxious stimulation applied to the right hind paw. Scale bar = 20 µm.