Neurons expressing neuropeptide Y mRNA in the infundibular hypothalamus of Japanese quail are activated by fasting and co-express agouti-related protein mRNA

Timothy Boswell, Qiushi Li, Sakae Takeuchi

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

The neural mechanisms involved in the compensatory hyperphagia exhibited by many vertebrate species after a fast are not fully understood but, in mammals, appear to involve nutritionally-sensitive neurons that co-express neuropeptide Y (NPY) and agouti-related protein (AGRP) in the infundibular hypothalamus. We investigated whether these neurons have been evolutionarily conserved in a non-mammalian vertebrate, the Japanese quail. Birds exhibited compensatory hyperphagia 1 h after return of food following a 24-h fast. We addressed a potential regulatory role for NPY, first, by using in situ hybridisation (ISH) to map NPY gene expression in the hypothalamus. This revealed a strong signal in the infundibular nucleus (IN). Secondly, we quantified NPY gene expression in 24-h fasted birds compared to ad libitum fed controls using two independent methods. In whole hypothalamus, measured by ribonuclease protection assay, NPY mRNA increased 1.5-fold in fasted birds. A similar, 1.7-fold, increase was observed specifically in the IN when analysed by ISH. No differences in NPY expression between fed and fasted birds were observed in other brain regions. To determine whether NPY neurons in the avian IN co-express AGRP, we cloned a fragment of the quail AGRP gene and used it to localise AGRP mRNA by ISH. The gene was expressed exclusively in the hypothalamus, specifically in the IN, where its distribution matched that of NPY. Double-label ISH revealed that the majority of NPY neurons in the IN co-express AGRP mRNA. Collectively, these data indicate that this cell type has been neuroanatomically and functionally conserved during vertebrate evolution.

Original languageEnglish
Pages (from-to)31-42
Number of pages12
JournalMolecular Brain Research
Volume100
Issue number1-2
DOIs
Publication statusPublished - Apr 30 2002

Keywords

  • Birds
  • Body weight
  • Brain
  • Food intake
  • Gene expression

ASJC Scopus subject areas

  • Molecular Biology
  • Cellular and Molecular Neuroscience

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