The sites of encephalic photoreception in photoperiodic induction of the growth of the testes in the White-crowned Sparrow, Zonotrichia leucophrys gambelii

Abstract

In bilaterally enucleated White-crowned Sparrows, Zonotrichia leucophrys gambelii, testicular growth and development at rates similar to those of intact birds subjected to long days, can be induced by illumination of sites within and near the ventromedial hypothalamus from the tips of single, chronically implanted, light-conducting fibers. Essentially identical results are obtained with the same mode of encephalic illumination of birds with intact eyes held on short days that are otherwise nonstimulatory. Examination of the distribution of the sites of the fibers from which weak illumination induced testicular growth, increase in plasma level of luteinizing hormone or increase in plasma level of testosterone suggests that most of the photoreceptors must lie either within the ventromedial hypothalamus or in sites ventral thereto, such as the tuberal complex. For the time being, at least, we find it necessary to assume that some photosensitive elements of the system occur outside of the ventral hypothalamus.

The system of cerebrospinal fluid-contacting neurons.

“…They may be identical to the so-called "deep encephalic photoreceptors" demonstrated in physiological experiments (for literature, see VIGH-TEICHMANN et al, 1976b;YOKOYAMA et al, 1978;OKSCHE and HARTWIG, 1979;CADUSSEAU and GALAND, 1981;HARTWIG and OKSCHE, 1982). In recent light and electron microscopic investigations, the cilia of mammalian pinealocytes and hypothalamic CSFcontacting neurons (paraventricular organ, infundibular nucleus and preoptic nuclei of the frog and newt; preoptic and periventricular nuclei of the European minnow, eel and rainbow trout; mammillary recess of the goldfish) did not show any significant antiopsin reaction by means of the PAP-reaction , c, 1982VIGH and VIGH-TEICHMANN, 1981;.…”

An immunocytochemical study of encephalic photoreceptors in three species of lamprey

“…Illumination of the head of blinded and pinealectomised lampreys still triggered body movements (Young 1935), and direct illumination of the hypothalamus caused testicular growth in blinded mallards (Benoit 1935a,b). In the 1960s, work on lizards and birds demonstrated that the regulation of circadian rhythms and the photoperiodic control of reproduction was mediated by extraretinal and extrapineal photoreceptors (for reviews, see Menaker and Underwood 1976;Yokoyama et al 1978). Local illumination of the brain in birds suggested that two areas of the basal brain (the basal hypothalamus and paraolfactory area) contain photoreceptors that contribute to the photoperiodic response (Oliver et al 1977(Oliver et al , 1980.…”

Regulatory mechanisms for the development of the migratory phenotype: Roles for photoperiod and the gonad

“…Previous studies using electrolytic lesions in GWCS and white-throated sparrows identified distinct neuroendocrine pathways linking the posterior median eminence of hypothalamus and anterior pituitary that inhibited both fattening, migratory restlessness and gonadal development (Kuenzel and Helms, 1967;Yokoyama et al, 1978). Administering testosterone reestablished fattening but had no effect on migratory restlessness.…”