The Expression Of C-fos Gene Induced By Light Stimulation In Hen Mesencephalon

The pathway of optical information in hen mesencephalon was investigated using c-fos method, to do some basic work for understanding the mechanism in the effect of light on egg-laying. In poultry production, light is one of the important environmental factors for maintaining the life of the animals. Scientific utilization of light can further enhance chicken's productive performance, for example: promoting chicken's growth and development, regulating sexual maturation, increasing egg production rate, fertility rate, hatching eggs eligible rate and so on. Poultry is one of vertebrate which is the most dependent on the visual system. Their visual system is mainly divided into two parallel processing pathways of visual information: the tectofugal pathway and the thalamofugal pathway. For poultry, the tectofugal pathway is more important than the thalamofugal pathway. In chicken's tectofugal visual pathway, the problems that whether different light stimulation induce functional activities of different neurons or what are the neurons involved in the transmission of a specific light information have not be known yet.Light stimulates retina and the information is transmitted through optic nerve to hypothalamus or directly permeating skull arrives in conarium. Hypothalamus produces and secretes GnRH, which passing through pituitary portal system to anterior portion of hypophsis, inducing secretion of LH and FSH. LH cooperating with FSH facilitates follicular maturation, promoting ovary to secrete estradiol. These hormones jointly constitute endocrine system dominating procreation enginery and effect genital organs growth. But it is still unclear that in the nervous system, how the light information was adjusted.In encephalon, connection among neurons is labyrinthine. The conventional method to trace nervous pathway cannot diplay the integrated light pathway, because it generally cannot trace by trans-neuron. But immediate early gene-c-fos can be induced and expressed through trans-synaptic activation. When central nervous system received inside and outside stimulation, the Fos protein of expressive products of c-fos gene can be as a resolving tag of a single neuron response.c-fos is one of main member of immediate early gene in protooncogene. Coulping extracellular information in intracellular gene transcription, c-fos is described as "third messenger " in cell nucleus. Under normal circumstance, c-fos gene is commonly present in central nervous system, highly conserves and expresses at very low level, while in case of stimulated situation, a transient expression will be rapidly made. The expression of c-fos gene is a sign of response of encephalon receving various stimulations. The expression of c-fos gene induced by ache stimulation in ducks' spinal cord is used as immunoreactive positive picture of the expression of c-fos gene induced by light stimulation in hen mesencephalon, primarily cognizing the distribution and morphology of Fos-like immunoreactive positive neuron in ducks' spinal cord. The expression of c-fos gene was induced by light stimulation in hen mesecephalon: unilateral eyes of hens were kept dark for seven days. Then they accepted light stimulation of 20 lx for 1.5 hours and dark adaptation 1.5 hours. After perfusion with fixative, their brains were removed from the skulls and were made into continuous paraffin sections. Using immunohistochemical method and Western Blot method, expression of c-fos gene in mesencephalon was examined. The result showed that a number of Fos-like immunoreactive positive neurons were observed in mesencephalon, being mainly present in left stratum griseum centrale (SGC) of tectum, isthmi pars principals (Imc, Ipc), nucleus semilunaris (SLu), nucleus isthmo-opticus (ION), nucleus mesencephalicus lateralis (pars dorsalis, MLd), nucleus raphes (RN), and nucleus nervitrochlearis (nIV). And the Fos-like immunoreaction positive neurons were predominantly distributed in Imc and Ipc of the left mesencephalon, and the differentia of the cell density and the percentage chart of Fos-like immunoreactive positive neurons were distinct. But few Fos-like immunoreactive positive neurons were observed in encephalon regions without receiving light stimulation. The results suggested that though the optical information is mainly conveyed to mesencephalon through the tectofugal pathway, the tectoisthmi circus also play an important role in this course. The non-visual photosensitivesystem and light cross-projection in the tectofugal visual pathway cause the few expression of c-fos gene in encephalon regions without receiving light stimulation.