The orexinergic synaptic innervation of serotonin- and orexin 1-receptor-containing neurons in the dorsal raphe nucleus.
Orexin/hypocretin has been well demonstrated to excite the serotonergic neurons in the dorsal raphe nucleus (DRN). We studied the morphological relationships between orexin-containing axon terminals and serotonin- as well as orexin-receptor-containing neurons in the dorsal raphe nucleus. Using immunohistochemical techniques at the light microscopic level, orexin A (OXA)-like immunoreactive neuronal fibers in the DRN were found to make close contact with serotonergic neurons, while some of the serotonergic neurons also expressed the orexin 1 receptor (OX1R). At the electron microscopic level, double-immunostaining experiments showed that the orexin A-like immunoreactive fibers were present mostly as axon terminals that made synapses on the serotonin- and orexin 1-receptor-containing neurons. While only axodendritic synapses between orexin A-containing axon terminals and serotonergic neurons were detected, the synapses made by orexin A-containing axon terminals on the orexin 1-receptor-containing neurons were both axodendritic and axosomatic. The present study suggests that excitation effect of orexin A on dorsal raphe serotonergic neurons is via synaptic communication through orexin 1 receptor.
Wang
Qing-Ping
QP
Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Koyama
Yoshimasa
Y
Guan
Jian-Lian
JL
Takahashi
Kazumi
K
Kayama
Yukihiko
Y
Shioda
Seiji
S
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D002450:Cell Communication / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D009479:Neuropeptides / Q000378:metabolism; D064446:Orexin Receptors; D000068797:Orexins; D011903:Raphe Nuclei / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000096:biosynthesis*; D012701:Serotonin / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure
C578627:Hcrtr1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D012701:Serotonin