The Journal of Neuroscience, October 1, 2002, 22(19):8684-8690
Gonads and Singing Play Separate, Additive Roles in New Neuron
Recruitment in Adult Canary Brain
Benjamín
Alvarez-Borda and
Fernando
Nottebohm
The Rockefeller University Field Research Center, Millbrook, New
York 12545
New neurons are constantly added to the high vocal center (HVC) of
adult male canaries, Serinus canaria. Singing and
testosterone (T) are known to promote this addition, but it is not
known whether either variable can act on its own and what is their
effect when acting together. We studied this question by castrating
adult male canaries in late summer and quantifying their song in early fall. Intact birds served as controls. A 5 d systemic treatment of
two daily injections of the cell birth marker 3H-thymidine
started 10 d after surgery. Twenty days after the first
3H-thymidine injection and for a period of 1 month, we
quantified the singing of all birds, which were then killed. Amount of
singing, syllable diversity, and song stability were similar in intacts and castrates. When castrates and intacts that sang comparable amounts
were compared, the number of 3H-labeled HVC neurons was 2.6 times higher in intacts than in castrates. In castrates with plasma T
levels that were undetectable, the mean amount of singing was
positively related to the number of new neurons. We suggest that
singing and gonadal factors promote, separately, the recruitment of new
neurons and that when they exert this effect together they do so in an
additive manner.
Key words:
songbirds; canary; testosterone; singing; neurogenesis; new neurons; HVC
Copyright © 2002 Society for Neuroscience 0270-6474/02/22198684-07$05.00/0
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