Widespread capacity for steroid synthesis in the avian brain and song system

Endocrinology. 2006 Dec;147(12):5975-87. doi: 10.1210/en.2006-0154. Epub 2006 Aug 24.


Steroids exert powerful effects on the brains and behavior of many species, but measures and manipulations of endocrine physiology in songbirds often reveal unexplained connections between steroids and the brain. The zebra finch song system, a sensorimotor neural circuit sensitive to steroids throughout life, organizes and functions largely in apparent independence from gonadally derived steroids. We tested the hypothesis that the zebra finch brain has the capacity for de novo steroidogenesis and that neurally synthesized steroids, neurosteroids, may impact the song system. Using multiple techniques, we demonstrate that the steroidogenic acute regulatory protein (StAR), cytochrome P450 side-chain cleavage (CYP11A1), and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase, the first three factors in the steroidogenic pathway, are expressed in both developing and adult zebra finch brain. Detailed expression mapping at posthatch d 20 (P20) and adult reveals widespread area-specific expression and coexpression patterns for steroidogenic acute regulatory protein, CYP11A1, and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase, which suggest neurosteroids may modulate multiple brain functions, including sensory and motor systems. Notably, whereas expression of other steroidogenic genes such as aromatase has been essentially absent from the song system, each of the major song nuclei express at least a subset of steroidogenic genes described here, establishing the song system as a potential steroidogenic circuit.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 3-Hydroxysteroid Dehydrogenases / genetics
  • 3-Hydroxysteroid Dehydrogenases / metabolism
  • Animals
  • Blotting, Northern
  • Brain / metabolism*
  • Cholesterol Side-Chain Cleavage Enzyme / genetics
  • Cholesterol Side-Chain Cleavage Enzyme / metabolism
  • Cloning, Molecular
  • DNA, Complementary / isolation & purification
  • Female
  • Gonads / metabolism
  • In Situ Hybridization
  • Male
  • Models, Biological
  • Nucleic Acid Amplification Techniques / methods
  • Organic Chemicals / pharmacology
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Songbirds / metabolism*
  • Songbirds / physiology*
  • Steroids / biosynthesis*
  • Tissue Distribution
  • Vocalization, Animal / physiology*


  • DNA, Complementary
  • Organic Chemicals
  • Phosphoproteins
  • Steroids
  • steroidogenic acute regulatory protein
  • SYBR Green I
  • 3-Hydroxysteroid Dehydrogenases
  • Cholesterol Side-Chain Cleavage Enzyme