HI Arwa,

I guess you were asking two questions here.

Regarding the membrane potential, it could be anywhere from - 60 mV to -70 mV. I heard that younger neurons tend to rest as less negative potential but have not tested this myself. 

For the solution to use in patching, neurobasal medium won't work unless you bubble it with 5% CO2 (similar to the conditions in the incubator). Plus, neurobasal is quite expensive to use. I prefer Hibernate E which has similar components to Neurobasal but instead bicarbonate, it uses MOPS as a buffer for pH. It seems to keep neurons healthy for a really long time outside the incubator. 

Hope this helps!

Hello, Arwa.

Huong Ha said correctly about membranne potential, but you also should count your junction potential, so at your voltage meter you may see from -55 to -40 mV.

Also some neurons have large Cl- currents after disruption of membrane, so they can be more negative than -70 mV

Dear Arwa:

Much depends on your recording conditions, age of cultures and neuronal type.

Recording conditions: Of course you can do your recordings in neuro-basal media but make sure that you know what are the concentrations of your main ions (Na+, K+, Cl-, Ca2+ and Mg2+). Based on these, you will need to calculate the junction potential and compensate it for accurate estimation of the membrane potential. Also, you may play around with your internal solution. In fact, if you are not going to do any wash-ins or wash-outs of drugs, recordings in cultured media is preferable.  

Age: Young (embryonic, 2-4 days after plating) neurons are typically depolarized (between -35 and -50 mV) but this gradually changes if cultures are healthy and maintained well. Typically, the resting potential of one week old cultured neurons ranges between -55 and -70 mV.

Neuronal type: Peripheral neurons (sensory and sympathetic cells tend to have more negative resting potentials as well as cholinergic neurons of the basal forebrain). Cerebellar granule cells in my hand were always more depolarized, but this could be due to pretty poor seal that forms with this cells. Others that I have tried (hippocampal and cortical)  rest as always somewhere between :)     

Hope this helps. If you will have problems, please contact me. Getting recordings in cultured neurons can be problematic. All the best.

Saak Ovsepian 

Thank you all