Sex differences in DHEA and estradiol during development in a wild songbird: Jugular versus brachial plasma

Author ORCID Identifier

http://orcid.org/0000-0001-8235-6411 : Oliver Love

Document Type

Article

Publication Title

Hormones and Behavior

Publication Date

6-1-2008

Volume

54

Issue

1

First Page

194

Last Page

202

Keywords

3beta-HSD, Aromatase, Avian, Bird, Brain, Dehydroepiandrosterone, Estrogen, European starling, Nestling, Neurosteroid, Ontogeny, Sex difference, Sexual differentiation, Song, Testosterone, Zebra finch

DOI

10.1016/j.yhbeh.2008.02.014

ISSN

0018506X

Abstract

Sexual differentiation of the brain has traditionally been thought to be driven by gonadal hormones, particularly testosterone (T). Recent studies in songbirds and other species have indicated that non-gonadal sex steroids may also be important. For example, dehydroepiandrosterone (DHEA) - a sex steroid precursor that can be synthesized in the adrenal glands and/or brain - can be converted into active sex steroids, such as 17β-estradiol (E2), within the brain. Here, we examine plasma DHEA and E2 levels in wild developing European starlings (Sturnus vulgaris), from hatch (P0) to fledging (P20). Blood samples were collected from either the brachial vein (n = 143) or the jugular vein (n = 129). In songbirds, jugular plasma is enriched with neurally-synthesized steroids and, therefore, jugular plasma is an indirect measure of the neural steroidal milieu. Interestingly, brachial DHEA levels were higher in males than females at P4. In contrast, jugular DHEA levels were higher in females than males at P0 and P10. Brachial E2 levels were higher in males than females at P6. Surprisingly, jugular E2 levels were not high and showed no sex differences. Also, we calculated the difference between brachial and jugular steroid levels. At several ages, jugular steroid levels were lower than brachial levels, particularly in males, suggesting greater neural metabolism of circulating DHEA and E2 in males than females. At a few ages, jugular steroid levels were higher than brachial levels, suggesting neural secretion of DHEA or E2 into the general circulation. Taken together, these data suggest that DHEA may play a role in brain sexual differentiation in songbirds. © 2008 Elsevier Inc. All rights reserved.

E-ISSN

10956867

PubMed ID

18423637

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