Effects of cold stress on the messenger ribonucleic acid levels of corticotrophin-releasing hormone and thyrotropin-releasing hormone in hypothalami of broilers

In this study, seventy 1-d-old male broiler chicks were randomly allocated to 10 groups to investigate the effect of cold stress on the messenger RNA (mRNA) levels of corticotrophin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH) in hypothalami. The chicks were maintained at 30 +/- 2 degrees C temperature and given free access to standard chow and water. Until 15 d old, the 6 treatment groups were maintained at 12 +/- 1 degrees C. Hypothalami were collected for the assessment of the mRNA levels by semiquantitative reverse transcription-PCR after stress termination. Cold stress significantly decreased the mRNA levels of CRH in 6 and 12 h treatment groups and significantly increased the mRNA levels of TRH in 1, 6, and 12 h treatment groups during acute cold stress. There were no significant differences in the mRNA levels of CRH and TRH among different control groups during chronic cold stress. However, chronic cold stress resulted in a significant increase of the mRNA levels of CRH and a significant decrease of the mRNA levels of TRH compared with the corresponding control groups. The results indicate that the 2 genes show different response to cold stress at the mRNA levels, and on the other hand, the different degree of cold stress also produces different effects on the identical gene.