Monoamine oxidase and acetylcholinesterase in the neurohypophysis of the hagfish, Eptatretus burgeri

The peripheral region of both dorsal and ventral walls of the neurohypophyseal sac of the hagfish, Eptatretus burgeri, showed strong monoamine oxidase (MAO) activity. Acetylcholinesterase (AChE) activity was detected only in the dorsal wall anterior to the infundibular stalk and in the ventral wall, except for the ependymal cells. AChE was not detected in the dorsal wall posterior to the stalk, where aldehyde-fuchsin-positive material is deposited. From these distribution patterns of MAO and AChE the identity of the structural specializations of the neurohypophysis are discussed as compared with distributions of MAO and AChE in the median eminence and the pars nervosa of higher vertebrates.