Article (Scientific journals)
Effects of Castration and Testosterone Treatment on the Activity of Testosterone-Metabolizing Enzymes in the Brain of Male and Female Zebra Finches
Vockel, A.; Prove, E.; Balthazart, Jacques
1990In Journal of Neurobiology, 21 (5), p. 808-25
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Abstract :
[en] Recently, we described the distribution of testosterone-metabolizing enzymes (i.e., aromatase, 5 alpha- and 5 beta-reductases) in the zebra finch (Taeniopygia guttata) brain using a sensitive radioenzyme assay combined to the Palkovits punch method. A number of sex-differences in the activity of these enzymes were observed especially in nuclei of the song-control system. The hormonal controls of these differences have now been analyzed by gonadectomizing birds of both sexes and by giving them a replacement therapy with silastic implants of testosterone (T). Five nuclei of the song system (Area X [X], nucleus magnocellularis of the anterior neostriatum [MAN], nucleus robustus archistriatalis [RA], nucleus intercollicularis [ICo], hyperstriatum ventrale, pars caudalis [HVc]) and three preoptic-hypothalamic areas (preoptic anterior [POA], periventricular magnocellular nucleus [PVM], and posterior medial hypothalamic nucleus [PMH]) were studied as well as other limbic and control non-steroid-sensitive areas. The activity of the 5 alpha-reductase was higher in males than in females for the five song-control nuclei and was not affected by the hormonal treatments. The overall activity of this enzyme was not sexually dimorphic in POA and PVM. It was higher in males than in females in intact birds only, and was reduced by gonadectomy and enhanced by T. The activity of the 5 beta-reductase was higher in females than in males in all nuclei of the song system and in POA, but was not influenced by the changes in T level. Both sex and treatment effects were observed in the control of aromatase. The production of estrogens was dimorphic (females greater than males) in RA and PMH. It was increased by T in POA, PVM, and PMH, and also in RA. These data show that some of the sex differences in T-metabolizing enzymes result from the exposure to different levels of T in adulthood (e.g., 5 alpha-reductase in POA and PVM or aromatase in PVM), whereas others persist even if birds are exposed to the same hormonal conditions. These are presumably the result of organizational effects of steroids. The steroid modulation of the aromatase might be related directly to the activation of sexual, aggressive, and nest-building behaviors, whereas the stable dimorphism in 5 alpha- and 5 beta-reductase observed in the nuclei of the song system might be one of the neurochemical bases of the sex differences in the vocal behavior of the zebra finch.
Disciplines :
Endocrinology, metabolism & nutrition
Zoology
Neurosciences & behavior
Author, co-author :
Vockel, A.
Prove, E.
Balthazart, Jacques  ;  Université de Liège - ULiège > Département des sciences biomédicales et précliniques > Biologie de la différenciation sexuelle du cerveau
Language :
English
Title :
Effects of Castration and Testosterone Treatment on the Activity of Testosterone-Metabolizing Enzymes in the Brain of Male and Female Zebra Finches
Publication date :
July 1990
Journal title :
Journal of Neurobiology
ISSN :
0022-3034
eISSN :
1097-4695
Publisher :
John Wiley & Sons, Hoboken, United States - New Jersey
Volume :
21
Issue :
5
Pages :
808-25
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 18 November 2009

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