Observation on the Influence of Changing Photoperiod on Spontaneous Wheel-Running Activity of Neonatally Pinealectomized Rats

Abstract
Spontaneous running activity of adult female rats with epiphysis cerebri removed within 24 hr after birth was markedly altered. The motor activity was decreased, was independent of the estrous cycle, and the animals adjusted more readily to a photoperiod change. (Endocrinology87: 38, 1970) EPIPHYSIS cerebri recognized by Galen as a separate organ more than 20 centuries ago has been considered by many to be merely a nonfunctional vestige of a primitive light-sensing “third eye,” found in some amphibians. Only recently have systematic studies been undertaken to study the functions of this organ. In 1960, Lerner et at. (1) isolated from cattle pineals a substance which caused lightening of frog skins, determined its structure and named the compound melatonin. To date the effect of melatonin to cause aggregation of melanin in amphibian melanocytes is the only physiological function established with certainty.

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