ISSN:
1432-0878
Keywords:
Encephalic photoreceptors
;
Hypothalamus
;
Photoperiodism
;
Birds
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 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. We are most grateful to several colleagues at the University of Washington for their generous assistance. Dr. R.B. Pinter, Department of Electrical Engineering and Zoology; Dr. M.M. Harnois, Department of Physics, and Dr. R.J. Spiger, Geophysics Program, made suggestions and rendered invaluable assistance with various aspects of the optical measurements. Dr. John C. Wingfield and Mr. Philip W. Mattocks kindly assayed the plasma samples for luteinizing hormone and androgens. We wish to express our most sincere thanks to Dr. H.-G. Hartwig, Giessen, for his advice and to Miss I. Lyncker, Giessen, for her conscientious editorial aid and careful typing of the manuscript.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00209132
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