Hello. I intend to simulate extracellular epileptogenesis-like conditions in microglia cultures. I concluded that the most well-fundamented and ready available way is to alter ionic concentrations. I decided to start with increasing extracellular potassium concentration to 10-12 mM.
For the in vitro model, I use RPMI 1640 glutamax medium, which already contains KCl 5.333 mM.
I intend to incubate the cells for a period with high K+ cocentration, incubate with normal medium once again and continue the experiment for a number of days more.
What would be the most correct way to increase the potassium concentration from 5.333 to 10-12 mM in this readymade medium?
Thank you for the attention
Your plan to raise K concentration from 5 to 10mM will change the resting potential from about -87mV to -69mV. That may not alter the electrical activity much. I'd probably try a range of K concentrations up to 100mM.
A common way to raise extracellular K concentration is to change the entire bath bathing the cells. in this situation, you could do an isosmolar substitution of KCl for NaCl in your stock extracellular bath solution. You will have to build a system for bath perfusion and exchange. There are many such systems to be found online. The alternative is to apply the high K solution with a puffer system. A popular, though expensive commercial system is the Picospritzer. Alternatively you can build a gravity fed system that can be activated manually or electronically with a solenoid valve (Lee Valve).