Expression of hypothalamic GnRH-I mRNA in the female turkey at different reproductive states and following photostimulation

Seong W. Kang, Aree Thayananuphat, Israel Rozenboim, James R. Millam, John A. Proudman, Mohamed E. El Halawani*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


In birds, changes in hypothalamic gonadotropin-releasing hormone-I (GnRH-I) content and release are correlated with reproductive stages. This study examined the distribution and expression level of GnRH-I mRNA in anatomically discrete hypothalamic nuclei throughout the turkey reproductive cycle and following photostimulation. GnRH-I mRNA expression was determined using in situ hybridization in non-photostimulated (NPS), egg-laying (LAY), incubating (INC) and photorefractory (REF) hens. Overall, GnRH-I mRNA expression was greatest in the nucleus commissurae pallii (nCPa) and around the organum vasculosum lamina terminalis (OVLT), with less expression observed in the nucleus septalis lateralis (SL), cortico-habenula cortico-septum area, and within the nucleus preopticus medialis. GnRH-I mRNA expression was significantly increased in nCPa, OVLT, and SL after NPS hens (6L:18D) were exposed to a 30 or 90 min pulse of light beginning 14 h after first light (dawn). GnRH-I mRNA abundance within nCPa, OVLT and SL was greater in LAY than in NPS and INC hens, while mRNA expression was least in REF hens. These results indicate that GnRH-I mRNA expression in birds is sensitive to light stimulation during the photosensitive period and can be used to more precisely characterize their different reproductive stages.

Original languageAmerican English
Pages (from-to)91-99
Number of pages9
JournalGeneral and Comparative Endocrinology
Issue number2
StatePublished - Apr 2006

Bibliographical note

Funding Information:
We thank I. C. Dunn for providing of cGnRH-I cDNA, and O. M. Youngren for comments on the manuscript. This research was supported by Research Grant No. US-3399-03C from BARD, The United States–Israel Bionational Agricultural Research and Development Fund.


  • Avian hypothalamus
  • GnRH-I mRNA expression
  • In situ hybridization
  • Photostimulation
  • Turkey reproductive cycle


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