Gene expression and neural circuit formation in the developing brain nuclei governing suckling and masticatory behavior.

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1) Expression of neuropeptide Y (NPY) mRNA in the developing brain nuclei controlling feeding behaviorNPY mRNA expression was examined by in situ hybridization in the developing brain nuclei controlling feeding behavior from day 2 to day 10 of postnatal age (PND2-10). NPY mRNA expression in the hypothalamic arcuate nucleus (ARC) was significantly higher in fasted group than control group at PND2, 7 and 10. NPY mRNA expression in the nucleus of the solitary tract was increased in fasted group compared to control group at PND2 but there was no difference at PND7 and 10. NPY mRNA expression in the ARC of fasted group was reduced by a s.c. injection of insulin (5U/kg) or leptin (2 mg/kg).2) Catechol O-methyltransferase (COMT) mRNA expression in neonatal hypothalamus and an implication of estrogen receptorsCOMT mRNA expression was observed in the hypothalamic suprachiasmatic nucleus (SCN) throughout its rostrocaudal extent at PND1 and 2, and the mRNA levels decreased gradually until PND16. COMT mRNA was predominantly localized to the ventral and medial parts of the SCN. Neonatal COMT mRNA expression in the hypothalamus was reduced by a s.c. injection of 17β-estradiol or bisphenol A, and these effects were blocked by co-administration of ICI182780, a selective estrogen receptor antagonist.3) Effects of soft food and tooth-loss on neurogenesis in the adult dentate gyrus (DG)Four-week-old mice were subjected to feed powder diet for 10 weeks with or without removal of molars. They received daily injection of bromodeoxyuridine (BrdU) at 14 weeks of age for 12 consecutive days. BrdU-positive DG cells in these mice showed larger reduction in number than in control at 5 weeks after the BrdU injection and the ratio of neurons to the BrdU-positive cells decreased in the molarless mice.