The brains were
removed, fixed, sectioned and an antiserum against c-fos applied to the tissue sections.As an example of the c-fos method, consider the search for brain regions activated during singing in the song bird, the zebra finch.
Males finches were induced to sing (put a female in the room and they do it of their own accord).
Some males were sacrificed before getting a chance to sing, others sang for 6 min. 24s before being sacrificed.
The brains were
removed, fixed, sectioned and an antiserum against c-fos applied to the tissue sections.
Two sensorimotor nuclei, with the names HVc and RA, showed a strong positive reaction to the c-fos antibody (C and D) relative to the control animals (A and B).
They could show that this c-fos induction was independent of auditory feedback, since it occurred in deafened birds that sang.
Note how the c-fos immuoreactivity is in small dots.
Closer magnification shows that these dots represent the nuclei of neurons, exactly where you would expect a transcription factor.