I have recently switched from patching immortalized cells to primary neurons. I measured the osmolarity of neurobasal media with B27 supplement, which we use to maintain our primary neuron cultures, and was suprised to see the osmolarity at such a relatively low level of ~240mOsm. I have also measured the osmolarity of the media that has been in contact with cells for 2-3 days and found it still relatively low at ~250-260mOsm. I pulled a paper on neurobasal media and read that neurobasal media was optimized with lower osmolarity as compared to immortalized culture media but I didn't see a reason why listed.
Why is neurobasal media optimized at such low osmolarity?
If one is trying to do do whole cell configuration patching on cells being maintained at this low osmolarity should one lower their bath and internal solutions to ~260 and ~250mOsm respectively? Or does one use traditional osmolarites for bath and internal solutions of 295 and 280mOsm respectively and not have concerns about cell volume changes?
Cheers and thanks for your thoughts!