Characterization of orexin A immunoreactivity in the rat area postrema.
The distribution of orexin A immunoreactivity and the synaptic relationships of orexin A-positive neurons in the rat area postrema were studied using both light and electron microscopy techniques. At the light microscope level, numerous orexin A-like immunoreactive fibers were found within the area postrema. Using electron microscopy, immunoreactivity within fibers was confined primarily to the axon terminals, most of which contained dense-cored vesicles. Both axo-somatic and axo-dendritic synapses made by orexin A-like immunoreactive axon terminals were found, with these synapses being both symmetric and asymmetric in form. Orexin A-like immunoreactive axon terminals could be found presynaptic to two different immunonegative profiles including the perikarya and dendrites. Occasionally, some orexin A-like immunoreactive profiles, most likely to be dendrites, could be seen receiving synaptic inputs from immunonegative or immunopositive axon terminals. The present results suggest that the physiological function of orexin A in the area postrema depends on synaptic relationships with other immunopositive and immunonegative neurons, with the action of orexin A mediated via a self-modulation feedback mechanism.
Guan
Jian-Lian
JL
Department of Anatomy, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Wang
Qing-Ping
QP
Kageyama
Haruaki
H
Kita
Tetsuro
T
Takenoya
Fumiko
F
Hori
Tomoko
T
Shioda
Seiji
S
D000818:Animals; D031608:Area Postrema / Q000378:metabolism* / Q000648:ultrastructure; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D046529:Microscopy, Electron, Transmission; D009479:Neuropeptides / Q000378:metabolism*; D000068797:Orexins; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins