I am wanting to do some patch clamp recordings on hippocampal CA1 interneurons but not sure the best way to identify them. I know I could go into the radiatum but from what I’ve seen, the majority of interneurons are in the pyramidal cell layer.
Any ideas on ways to identify interneurons from pyramidal cells that don’t involve me patching the cell to check for intrinsic properties? Is there a way to stain fresh tissue and still use it for patch clamping?
Hi Chad,
Not sure if you are able to do this on your rig (or add it if not), but if you can use fluorescence there's many mouse lines that report different interneuron populations. GIN is a pan-interneuron reporter that would probably work well for you, or you could target PV, SST, NPY, VIP, etc INs specifically with CRE Lox recombination and floxed reporters, or BAC lines.
You could also quickly probe for FSIs with cell attached protocols before targetting them for wcr!
The chance to identify a non-pyramidal cell within the pyramidal cell layer based on shape is low and no referee would believe you without providing some sort of a proof (Electrophysiological or other...). An AP profile would be acceptable. So, you can either follow Alberto's advise if you have access and/or can afford technology based on fluorescent cells OR I am afraid, you have no choice but use the Current Clamp first. it would take you 3-4 minutes tops.1/ Run a quick protocol (say -50 to +250 pA in 25 or 50 pA increments lasting about 500 ms). 2/ that's it: based on the firing pattern, you have now identified your cell . You can then switch to V-Clamp and finish your experiment. That's quite a powerful tool available to you at no extra cost. All the best.
BTW, you can refer to many papers out there, one of them is (Article Lack of Depolarization-Induced Suppression of Inhibition (DS...
)even-though it's not about the hippocampus but contain references to other papers dealing with that area of the brain.
Hi Alberto and Fouad,
I appreciate the replies. This what I had expected. Truthfully I was interested in ways to identify these cell types outside of doing stereotaxic viral injections or a ‘guess and check‘ method. Perhaps this is why interneurons are so understudied...it’s time-consuming and difficult.
I think for now the plan is to patch and probe for AP firing properties. Then backfill with neurobiotin and reconstruct.
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