Electron-microscopic investigations of vasoactive intestinal peptide (VIP)-like immunoreactive terminal formations in the lateral septum of the pigeon

• Published in: Cell and tissue research 1994-11, Vol.278 (2), p.415-418
• Main Authors: Hirunagi, K, Kiyoshi, K, Adachi, A, Hasegawa, M, Ebihara, S, Korf, H W
• Format: Article
• Language: English
• Subjects: Animals; Cerebral Ventricles - chemistry; Cerebral Ventricles - ultrastructure; Columbidae - anatomy & histology; Golgi Apparatus - ultrastructure; Microscopy, Electron; Microscopy, Immunoelectron; Mitochondria - ultrastructure; Neurons - chemistry; Neurons - ultrastructure; Presynaptic Terminals - chemistry; Presynaptic Terminals - ultrastructure; Vasoactive Intestinal Peptide - analysis; Vasoactive Intestinal Peptide - immunology
• ISSN: 0302-766X; 1432-0878
• DOI: 10.1007/BF00414184

Vasoactive intestinal peptide (VIP)-like immunoreactive terminal fields were examined in the lateral septum of the pigeon by means of immunocytochemistry. According to light-microscopic observations, these projections originated from VIP-like immunoreactive cerebrospinal fluid (CSF)-contacting neurons, which are located in the ependymal layer of the lateral septum and form a part of the lateral septal organ. The processes of these cells gave rise to dense terminal-like structures in the lateral septum. Pre-embedding immuno-electron microscopy revealed that VIP-like immunoreactive axon terminals had synaptoid contacts with perikarya of small VIP-immunonegative neurons of the lateral septum, which were characterized by an invaginated nucleus, numerous mitochondria, a well-developed Golgi apparatus, endoplasmic reticulum and a small number of dense-core vesicles (about 100 nm in diameter). VIP-like immunoreactive axons were also seen in contact with immunonegative dendrites in the lateral septum. In both axosomatic and axodendritic connections, VIP-like immunoreactive presynaptic terminals contained large dense-core vesicles, clusters of small vesicles and mitochondria. These findings suggest that VIP-immunoreactive neurons of the lateral septal organ project to small, presumably peptidergic nerve cells of the lateral septum and that the VIP-like neuropeptide serves as a neuromodulator (-transmitter) in this area.