This may seem like a silly textbook question but I'm not an expert and I'm really confused. I culture organotypic hippocampal cultures (stopinni) and I'm having problems distinguishing visually where the CA1 is and where the subiculum starts. I read that the subiculum is where the cell bodies start to widen. I have attached a drawing which I think is easier than explaining in words. It's drawn in pait...sorry if it's really poor quality. Anyhow, the cell layer starts to widen anywhere along the transverse axis and it varies between tissue samples. Again, I know this is a text book question, but it's important to my research because I'm doing ischemic-type situations to which the CA1 is especially vulnerable. I find that when chemically depolorizing the culture with potassium that it is the widened part that is damage and nothing before it, which makes me wonder what the widened part is - subiculum or CA1 still?

Any help would be greatly appriciated!!!

Before I explain anything I need to know which age group of animal you prefer for slices, is it very young?
Because the structure you have shown looks like that slices are immature.
Is this pictorial representation is of your slice and and do you use mice ? or rat?
Just for clarification is there an open slit the wide area you have shown which follows CA1 in one slice and is in the mid of CA1 in other slice.

The subiculum is almost when a fine cell body layer(pyramidal) gets over i.e; CA1 .

You can further get more clarification if you need, as I also isolate CA1 region.

I hope these two images will make you clear.