Pineal Role in the Duck Extraretinal Photoreception

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Abstract
The testicular effects of the direct illumination of the pineal area were studied in blinded ducks by evaluating the plasma levels of testosterone and the activity of 3β-hydroxysteroid dehydrogenase-4-5-ene-isomerase, 6β- and 17αhydroxylase and 5α-, 17β- and 20α-reductases. Prepuberal ducks were divided in 4 groups: I) Blinded; II) Blinded plus continuous illumination of the pineal area; III) Like II except that the lamp was painted, and IV) Like II plus pinealectomy. Ducks were placed in darkness for 1 month after which they were sacrificed. Direct illumination of the pineal region stimulated the testicular function, except for the 5α-reductive pathway, which was inhibited. Pinealectomy diminished significantly the effects of light on the plasma levels of testosterone and the testicular 3P-hydroxysteroid dehydrogenase-4-5-ene-isomerase, 17β-reductase, 17α-hydroxylase and 5α-reductive pathway. The black-painted lamp produced a testicular stimulation which was significantly lower than that observed in the pinealectomized-illuminated group. These results make it clear that the pineal gland is an important component of a multiple extraretinal photoreceptor system, but also demonstrate that this gland is not the exclusive site of extraretinal light perception. (Endocrinology91: 1318, 1972)

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