DIFFUSION BETWEEN THE NEUROHYPOPHYSIS AND THE ADENOHYPOPHYSIS OF LAMPREYS, PETROMYZON-MARINUS

Horseradish peroxidase (HRP), a protein that can be visualized by appr opriate histochemical procedures, was injected into the third ventricl e of the brain of adult lampreys, Petromyzon marinus. Within 5 to 15 m in HRP had passed through the neurohypophysis, which forms the floor o f the third ventricle. It appeared at this time to have diffused throu ghout the connective tissue separating the adenohypophysial follicles from the neurohypophysis and from each other. This observation would i ndicate that it is possible for neurosecretory peptides like gonadotro pin-releasing hormone to diffuse from the brain (neurohypophysis) to t he adenohypophysis and thus regulate its secretory activity in lamprey s. (C) 1994 Academic Press, Inc.