Synaptic interaction between ghrelin- and ghrelin-containing neurons in the rat hypothalamus.
Synaptic relationships between ghrelin-like immunoreactive axon terminals and other neurons in the hypothalamic arcuate nucleus (ARC) were studied using immunostaining methods at the light and electron microscope levels. Many ghrelin-like immunoreactive axon terminals were found to be in apposition to ghrelin-like immunoreactive neurons at the light microscopic level. At the electron microscopic level, ghrelin-like immunoreactive axon terminals were found to make synapses on ghrelin-like immunoreactive cell bodies and dendrites in the ARC. While the axo-dendritic synapses between ghrelin- and ghrelin-like immunoreactive neurons were mostly the asymmetric type, the axo-somatic synapses were both asymmetric and symmetric type of synapses. Ghrelin at 10(-10) M increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) in the neurons isolated from the ARC, some of which were immunocytochemically identified as ghrelin-positive. Ghrelin at 10(-10) M also increased [Ca(2+)](i) in 12% of ghrelin-like immunoreactive neurons in the ARC. These findings suggest that ghrelin serves as a transmitter and/or modulator that stimulates [Ca(2+)](i) signaling in ghrelin neurons of the ARC, which may participate in the orexigenic action of ghrelin. Our data suggests a possibility of existing a novel circuit implicating regulation of feeding and/or energy metabolism.
Hori
Yasunori
Y
Department of Biochemical Toxicology, School of Pharmaceutical Sciences, Showa University, Tokyo 142-8555, Japan.
Kageyama
Haruaki
H
Guan
Jian-Lian
JL
Kohno
Daisuke
D
Yada
Toshihiko
T
Takenoya
Fumiko
F
Nonaka
Naoko
N
Kangawa
Kenji
K
Shioda
Seiji
S
Yoshida
Takemi
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D048430:Cell Shape; D054439:Ghrelin / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure
D054439:Ghrelin; D002118:Calcium