I'll answer myself in case someone else is interested in the same
question later. I found an article by Olbrich and Braak (1985) in Anat.
Embryol. 173:105-110 stating that in the human hippocampal area CA1 less
than 10% of the neurons are not pyramidal cells. They also cite similar
results for rats and monkeys in the discussion section.
Thus I think one can estimate that the rat CA1 (of a single hippocampus)
has approx. 355.000 pyramidal cells.
hthsl (hope this helps someone later ;)
Mathias
