Long-Lasting Effect of Changes in Incubation Temperature on Heat Stress Induced Neuronal Hypothalamic c-Fos Expression in Chickens

In birds, during prenatal 'critical periods' the thermoregulatory system can be life-long imprinted by the actual incubation temperature. The aim of the present study is to elucidate long-term effects of prenatal temperature experiences, applied at the end of incubation, on central thermoregulatory mechanisms by detection of neuronal hypothalamic c-Fos expression as a consequence of acute heat stress in growing and adult chickens using immunohistochemistry. From day 18 of incubation chicken embryos were incubated in three temperature groups: 37.5°C (regular incubated), 34.5°C (cold incubated) or 38.5°C (warm incubated). C-Fos expression was detected in 29 4-weeks old and 61 8-weeks old chickens after acute heat stress (42°C for 90 min). The results show, that prenatal temperature experiences can induce long-lasting changes in the heat induced neuronal hypothalamic c-Fos expression. But significant alterations could be only found in 8 weeks old chickens and these changes were in opposite as expected. It means that after acute heat stress cold incubated chickens have a significantly lower neuronal c-Fos expression compared with the warm incubated ones. This effect could be caused by cross adaptation to the actual ambient temperature during the growing period. Further, the developmental pattern of the hypothalamic neuronal network in different incubated birds, which is demonstrated by neuronal c-Fos expression in the actual study, is similar to the pattern, which we found after recordings of single neurons activity, to a higher extent. Correlations between both parameters, which are involved in neuronal plasticity, can be accepted.