CHRONOBIOLOGIC STUDY IN DOMESTIC DUCK .2. PHYSIOLOGICAL MECHANISM OF CHRONOBIOLOGIC ACTION OF VISIBLE-LIGHT ON GONADS OF MALE DUCK

  • 1 January 1978
    • journal article
    • research article
    • Vol. 5  (2) , 158-168
Abstract
The light stimulates the chain formed by the retina, the optic nerve, the hypothalamus and the anterior part of the pituitary. This chain includes 2 photo-receptors, a superficial one, the retina and a deep one, the hypothalamus. The retina was only sensitive to orange and red rays. Consequently an autonomic retina intervenes instead of the visual retina. The hypothalamus was sensitive to all visible rays when they were brought directly in contact with it through a quartz rod placed in the orbit which was previously emptied. The hypothalamus was more than 100 times more sensitive than the retina. This great sensitivity allows normal stimulation by the most penetrating rays in the orbital region. UV and IR rays were inactive on the autonomic retina and on the hypothalamus. The neurosecretory cells of the latter, stimulated directly or indirectly, secrete hormones which reach a capillary network covering the median eminence via the axones. By portal veins hypothalamic hormones reach the anterior part of the pituitary, that stimulates secretion of hormones, which reach the corresponding target organs and in particular the gonads through the systemic circulation. It is a neuro-hormonal mechanism which the external factor light, brings into play to stimulate various functions of the autonomic life of the organism.

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