Sexually dimorphic neuron addition to an avian song-control region is not accounted for by sex differences in cell death
✍ Scribed by Burek, M. J. ;Nordeen, K. W. ;Nordeen, E. J.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 174 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0022-3034
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✦ Synopsis
Only male zebra finches sing, and acts on some HVC neurons before they complete their several brain regions implicated in song behavior exmigration and/or early differentiation. Although the hibit marked sex differences in neuron number. In one migratory route of HVC neurons is not known, a large region, the high vocal center (HVC), this dimorphism number of E 2 receptor-containing cells (ER cells) redevelops because the incorporation of new neurons is side just ventromedial to the HVC and adjacent to the greater in males than in females during the first sevproliferative ventricular zone. Next, we investigated eral weeks after hatching. Although estrogen (E 2 ) exwhether these ER cells contribute to early-arising sex posure stimulates neuron addition in females, it is not differences in HVC neuron addition. By combining known where (E 2 ) acts, or to what extent sexual differ-[ 3 H]thymidine autoradiography with immunocytoentiation influences the production, specification, or chemistry for ERs, we first established that ER-exsurvival of HVC neurons. In the present study we first pressing cells are not generated during posthatch sexreassessed sex and (E 2 )-induced differences in cell deually dimorphic HVC neuron addition, and thus are generation within the HVC using the TUNEL technot young HVC neurons that transiently express ERs nique to identify cells undergoing DNA fragmentation during their migration. Furthermore, in 25-day-old indicative of apoptosis. HVC neuron number, as well
birds we found no sex difference in the density of as the density and number of TUNEL-labeled and pyknotic cells among this group of ER cells, suggesting pyknotic cells within the HVC were measured in northat these cells do not promote the differential survival mal 20-and 30-day-old males and females, and in 30of HVC neuronal precursors migrating through this day-old females implanted with E 2 on posthatch day region. Rather, ER cells or other cell populations may 18. Although HVC neuron number was greater in establish sex differences in HVC neuron number by males than in females, and was masculinized in E 2 creating dimorphisms in cellular specification. ᭧ 1997 females, no group differences were evident in the abso-