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A. NK-ir perikarya (arrows) and fibers (arrowheads) in the periaqueductal gray (PAG). D: dorsal; M: medial. Scale bar: 100 μm B. A low density of immunoreactive fibers is observed in layer 1 of the superior colliculus (SC), whereas a high density is located in layer 2. D: dorsal; M: medial. Scale bar: 100 μm
