Wang Qing-Ping, Guan Jian-Lian, Matsuoka Takashi, Hirayana Yumi, Shioda Seiji
Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Peptides. 2003 Jun;24(6):925-30. doi: 10.1016/s0196-9781(03)00158-x.
The ultrastructure and the synaptic relationships of the orexin-A-like immunoreactive fibers in the dorsal raphe nucleus were examined with an immunoelectron microscopic method. At the electron microscopic level, most of the immunoreactive fibers, a varicosity appearance at the light microscopic level, were found as axon terminals. The large dense-cored vesicles contained in the immunoreactive axon terminals were the most intensely immunostained organellae. These axon terminals were often found to make synapses. While the axo-dendritic synapses were usually asymmetric in appearance, the axo-somatic synapses were symmetric. Orexin-A-like immunoreactive processes with no synaptic vesicles were also found. These processes often received asymmetric synapses. With less frequency, the synapses were found between the orexin-like immunoreactive processes. The results suggest that the orexin peptides are stored in the large dense-cored vesicles; the orexin-containing fibers may have influences on the physiological activities of the dorsal raphe nucleus through direct synaptic relationships.
