retina spike in rabbit

Dear sir,

I used MEA system to record light response of rabbit retina. The MEA probe used is standard MEA(200/10-ITO), and the amplifier is MEA1060-BC-PA.
As perfusion, the background noise was about ±20µV. I can see the field potential, but not any spike. I read the MC_Rack tutorial and found the spike is about ±20µV while noise is only ±10µV. So I think there are two possibilities:
(1) the noise is too large, so I can't see any spike. (and I also wanna know how large is ganglion cell spike in generally)
(2) the contact between retina and MEA probe is not good
I really need some information, and appreciate your help.

Yu Ting, Huang

Dear Huang Yu Ting,
I asked some retina experts I know, they claimed that ganglion cell spikes should usually be larger then 100µV. They suspect a problem with the preparation or with the contact. The MEA must be coated, e.g. with PDL. They suggested to have a look at this paper:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3107248/pdf/pone.0020810.pdf

Best regards Frank MCS

Dear Frank,

Thanks for your suggestion. I have another question. Is it necessary to hydrophilize the MEA probe before coating?
Thanks again.

Yu-Ting

Dear Yu-Ting,
hydrophilization is always helpful, but not absoluterly necessary. So if you have the option to hydrophilize the MEAs I would do so, otherwise the stroage in water as described in the MEA cleaning guide should be sufficient.

Best regards Frank MCS

Dear Frank,

Thanks for your suggestion. I have coated the MEA probe with nitrocellulose and covered retina with net,
and then I could recorded the spontanous activity of retina. However, when I gave a light stimulus to retina,
I only recorded field potential but no spike of ganglion cell. Could you give me some advice?
Thank you very much.

Yu-Ting

Dear Yu-Ting,
I am no retina expert, so I can't help you further unfortunately. I would check the literature on our website and get in touch with somebody working in the field. For example, the group of Thomas Münch in Tübingen here in Germany is very experienced.

Best regards Frank