| A proto-oncogene, c-fos, as an immediate early gene is extensively present in the neurons in the central nervous system (CNS). However, its expression is so weak that it can not be detected in the normal condiction. Many stimulation can induce its rapid expression in some neurons in CNS. The expression product of c-fos has been viewed as a cellular marker of neural activity to identify activated neurons in CNS. Accordance to the responses, a pathway to the stimulation in the CNS can be outlined. In this study, the responses of hen brain to light stimulation in different intensities were observed using c-fos method. After wearing a blinder for 7 days, the right eyes received a light stimulation of different intensities (10Lux, 20Lux, 30Lux and 40Lux). After a dark adaptation for 1.5 h, the brains were removed from the skulls after perfusion. Serial paraffin sections were made and underwent a immunohistochemistric staining and in situ hybridization for Fos protein to test the expression of c-fos gene induced by light stimulation. At the same time, the existence of Fos protein was detected by Western blot method. According to the appearing manner, location and quantity of Fos protein, analyse the transmission pathway of optical information, providing some valuable data to the further elucidate the forming mechanism of the avian visual sense, so as to do some basic work for illuminating the mechanism in the effect of light on egg-laying, maximally to utilize the light for increasing the egg-layings in poultry production. By the Fos protein in the different light intensities on the same expression in the different day-old hens to determine the same-day-old hen brain stimulation of different intensity of reaction to light, to explore the light on the production performance of hens mechanism for the poultry industry, the scientific provide a theoretical basis for the use of light Gonadotrophin releasing hormone (GnRH) immunoreactive neurons were also observed to investigate the relationship between the the light stimulation and the reproductive activity in hen brain. The results showed that a number of Fos-like immunoreactive positive neurons were observed in hen mesencephalon and diencephalon after a light stimulation, being mainly present in left stratum griseum centrale (SGC) of tectum, isthmi pars principais (Imc, Ipc), nucleus rotundus (ROT), nucleus geniculatus lateralis pars ventralis (GLv), paraventricular nucleus (PVN), and arcuate nucleus (ARC) and nucleus nervi oculomotorii (OMv). Positive cell count compared with the control group significant difference (p <0.010).The expression of c-fos gene was varied with the different intensity light stimulation in hen, the immunoreactive intensity was the highest in 20Lux, 30Lux group, secondary in 40Lux, the lowest in 10Lux group within SGC, ROT, SLu, Glv, Imc, Ipc. That was highest in 20Lux, 30Lux and 40Lux group gradually weakened within PVN, ARC. The immunoreactive intensity was increased with the intensity of light within OMc. It indicated that the responses in central nervous system to the different intensity light stimulation were different . In situ hybridization method to detect hen's brain between the brain and in a large number of Fos-like immunoreactive neurons were mainly seen in the left side, being mainly present in left stratum griseum centrale (SGC) of tectum, isthmi pars principais (Imc, Ipc), nucleus rotundus (ROT), nucleus geniculatus lateralis pars ventralis (GLv), paraventricular nucleus (PVN), and arcuate nucleus (ARC). And the result of western blotting showed that obviously there is specific a band between the bands of 49kD to 90 kD. The band is correspond to the Fos protein band. It proves the Fos protein being in the extract of brains. It indicated that chick tectofugal pathway is not only the processing of visual information, but also is sensive to light stimulation. A lateral path of this pathway, tectoisthmi circus, take part in the transmission and processing of optical information too. The responses in central nervous system to light stimulation were different at different intensity of light. Light stimulation may regulate the reproductive function by influence secretion and content of GnRH in the nuclei in the pathway of optical information.
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