Orexin action on oxytocin neurons in the paraventricular nucleus of the hypothalamus.
Oxytocin neurons in the paraventricular nucleus (PVN) of the hypothalamus play an important role in food intake regulation. It has been shown that the secretion of oxytocin from the hypothalamus shows a diurnal circadian rhythmic pattern and disturbance of this pattern leads to the development of obesity. However, whether oxytocin secretion from the PVN has a diurnal pattern remains unknown. Here, we show that oxytocin secretion from the PVN does have a diurnal pattern and that the terminals of orexin neurons, the neuropeptide responsible for regulating the sleep-wake rhythm, are synapsed with PVN oxytocin neurons. Using transgenic rats selectively expressing monomeric red fluorescent protein 1 in oxytocin neurons, we found that orexin-A inhibits the activities of PVN oxytocin neurons by inhibiting glutamatergic excitatory synaptic input. These data suggest that orexin is a possible candidate to regulate the circadian rhythm of PVN oxytocin neurons. The circadian rhythmic secretion of oxytocin is considered to play an important role in maintaining homeostasis, including body weight regulation. Our present data indicate a possible contribution of orexin toward the development of circadian rhythm in PVN oxytocin neurons.
Departments of aMedical Electrophysiology bOrgan Regulatory Surgery, Fukushima Medical University School of Medicine, Fukushima cTakasu Clinic, Nagoya dDepartment of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Yuko
Y
Maejima
Shinichi
S
Takahashi
Katsuya
K
Takasu
Seiichi
S
Takenoshita
Yoichi
Y
Ueta
Kenju
K
Shimomura
D000818:Animals; D002491:Central Nervous System Agents / Q000494:pharmacology; D004435:Eating / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000068797:Orexins / Q000378:metabolism* / Q000494:pharmacology; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D055647:Rats, Transgenic; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D046509:Tissue Culture Techniques; D000521:alpha-MSH / Q000378:metabolism; D000097573:Red Fluorescent Protein
D002491:Central Nervous System Agents; D018698:Glutamic Acid; D008164:Luminescent Proteins; D000068797:Orexins; D010121:Oxytocin; D000521:alpha-MSH; D000097573:Red Fluorescent Protein