[Electron microscopic study of the peptidergic neurosecretory cells of the preoptic nucleus of carp].

The preoptic neurosecretory cells (NSC) in sexually mature female Cyprinus carpio L. have been studied with electron microscope in winter. Separate weakly differentiated NSC and differentiated NSC of small and mean size are localized in the ventral part of Nucleus preopticus. The big highly differentiated NSC are mostly localized in the dorsal part of Nucleus preopticus. Among these types of the cells are established the light and dark forms. The "picnomorphic" cells are found only in the dorsal part of Nucleus preopticus. The light NSC are subdivided into two following kinds of cells: 1. NSC with a great amount of moderately dilated channels of the rough endoplasmic reticulum and scarce neurosecretory granules; 2. NSC with a small amount of narrow channels of the rough endoplasmic reticulum and many neurosecretory granules. The various types of differentiated NSC reflect the asynchronous formation of neurosecretory granules. The Nucleus preopticus of C. carpio has mostly the light highly differentiated NSC. It is supposed that most of the NSC in Nucleus preopticus produce and storage neurosecretory granules.