Are there indications for a granule-free form of vasopressin?

Following a short immobilization the supraoptic perikarya exhibit peroxidase-antiperoxidase (PAP)-labeled rough endoplasmic reticulum and the intercellular clefts in the basal nuclear area are distinctly labeled by PAP molecules. The fibers in this basal part of the supraoptic nucleus as well as those of the internal zone of the median eminence, beside few polymorphic, positively strained granules, contain a labeled tubular network or free PAP on fuzzy material.