Neuronal interaction between melanin-concentrating hormone- and alpha-melanocyte-stimulating hormone-containing neurons in the goldfish hypothalamus.
Intracerebroventricular (ICV) administration of melanin-concentrating hormone (MCH) inhibits food intake in goldfish, unlike in rodents, suggesting that its anorexigenic action is mediated by alpha-melanocyte-stimulating hormone (alpha-MSH) but not corticotropin-releasing hormone. This led us to investigate whether MCH-containing neurons in the goldfish brain have direct inputs to alpha-MSH-containing neurons, using a confocal laser scanning microscope, and to examine whether the anorexigenic action of MCH is also mediated by other anorexigenic neuropeptides, such as cholecystokinin (CCK) and pituitary adenylate cyclase-activating polypeptide (PACAP), using their receptor antagonists. MCH- and alpha-MSH-like immunoreactivities were distributed throughout the brain, especially in the diencephalon. MCH-containing nerve fibers or endings lay in close apposition to alpha-MSH-containing neurons in the hypothalamus in the posterior part of the nucleus lateralis tuberis (NLTp). The inhibitory effect of ICV-injected MCH on food intake was not affected by treatment with a CCK A/CCK B receptor antagonist, proglumide, or a PACAP receptor (PAC(1) receptor) antagonist, PACAP((6-38)). ICV administration of MCH at a dose sufficient to inhibit food consumption also did not influence expression of the mRNAs encoding CCK and PACAP. These results strongly suggest that MCH-containing neurons provide direct input to alpha-MSH-containing neurons in the NLTp of goldfish, and that MCH plays a crucial role in the regulation of feeding behavior as an anorexigenic neuropeptide via the alpha-MSH (melanocortin 4 receptor)-signaling pathway.
Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan.
Sei-Ichi
S
Shimakura
Kenji
K
Kojima
Tomoya
T
Nakamachi
Haruaki
H
Kageyama
Minoru
M
Uchiyama
Seiji
S
Shioda
Akiyoshi
A
Takahashi
Kouhei
K
Matsuda
D000818:Animals; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D006054:Goldfish; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D008543:Melanins / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology; D010907:Pituitary Hormones / Q000378:metabolism*; D011377:Proglumide / Q000494:pharmacology; D000521:alpha-MSH / Q000378:metabolism*
D007028:Hypothalamic Hormones; D008543:Melanins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010907:Pituitary Hormones; D000521:alpha-MSH; C019463:melanin-concentrating hormone; D011377:Proglumide