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3B-HSD expression in the CNS of a Manakin and Finch

  • Author(s): Eaton, Joy D.
  • Advisor(s): Schlinger, Barnett
  • Micevych, Paul
  • et al.
Abstract

DHEA (dehydroepiandrosterone) can circulate at relatively high levels with a variety of reported actions on the central nervous system (CNS). Some of these actions require the conversion of DHEA into more active steroidal metabolites catalyzed by the enzyme 3-HSD. Whereas DHEA is often measured in blood, efforts to evaluate neural 3-HSD are limited. A role for neural 3-HSD has been demonstrated in some non-breeding oscine songbirds when DHEA promotes aggressive behavior, most likely after its neural conversion into active androgens and estrogens. Our lab studied courtship behavior of male Golden-Collared Manakins (Manacus vitellinus) and found that low levels of courtship persist when circulating testosterone levels are basal. Therefore, we tested the hypothesis that DHEA might activate behavior in these sub-oscine birds by determining if DHEA is measurable in blood and by evaluating 3-HSD expression in the brain and spinal cord. For comparison, we examined 3-HSD expression in similar CNS tissues of zebra finches, an oscine species in which plasma DHEA and neural 3-HSD expression have been reported previously. DHEA was detected in manakin blood at levels similar to that seen in other species. Although 3-HSD was present in all finch brain regions examined, 3-HSD was expressed only in the manakin hypothalamus where it was present at relatively high levels. In the spinal cord, 3-HSD was detected in some but not all regions examined in both species. These data indicate that manakins have the neural machinery to convert circulating DHEA into potentially active androgens and/or estrogens.

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