Photomicrograph of met-enkephalin immunoreactivity in the globus pallidus (A) and (B), the periaqueductal gray (C) and (D) and the dentate gyrus of the hippocampal formation (E) and (F) in animals without colchicine pretreatment (A), (C), and (E) or with 200 µg of colchicine (B), (D), and (F). Measure bar =10 µm for all photomicrographs.