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      Lighting Conditions Affect Testosterone Feedback Sensitivity in Castrated Rats

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          Abstract

          It has been shown in the Syrian hamster that a short photoperiod sensitizes the hypothalamo-hypophyseal axis of castrated animals to the negative feedback effect of testosterone. There is some evidence that even the reproductive system of the rat, which is generally considered not to be very sensitive to light, can respond to changes in illumination. Therefore, we found it of interest to examine whether alterations in lighting conditions produce changes of sensitivity in the negative feedback effect of testosterone in the rat. We kept intact, castrated, and castrated testosterone-treated animals either in periodic (L:D 12:12) or constant light for 7 days starting 4 weeks after castration. In all 3 testosterone-injected groups, serum luteinizing hormone (LH) was lower in constant than in periodic light. Exogenous testosterone did not decrease the castration-induced elevations of pituitary LH and folliclestimulating hormone (FSH). On the contrary, testosterone increased the pituitary contents of LH and FSH, especially in constant light. We conclude that, in constant light, the hypothalamo-hypophyseal axis of the castrated rat becomes more sensitive to the negative feedback action of testosterone.

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          Author and article information

          Journal
          HRE
          Horm Res Paediatr
          10.1159/issn.1663-2818
          Hormone Research in Paediatrics
          S. Karger AG
          1663-2818
          1663-2826
          1989
          1989
          02 December 2008
          : 31
          : 4
          : 184-189
          Affiliations
          Institute of Physiology, University of Helsinki, Finland
          Article
          181113 Horm Res 1989;31:184–189
          10.1159/000181113
          2507436
          © 1989 S. Karger AG, Basel

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          Page count
          Pages: 6
          Categories
          Original Paper

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