High-throughput measurements of neuronal activity in single human iPSC-derived glutamate neurons

Induced pluripotent stem cell (iPSC)-derived neurons provide a promising platform for studying neuronal function and modeling central nervous system (CNS) diseases. However, functional analysis of large populations of iPSC-derived neurons has been challenging. Here, we developed a high throughput strategy targeting N-methyl-D-aspartate receptors (NMDA-R) to enhance neuronal activity and reveal functional phenotypes in human iPSC-induced glutamatergic neurons (iGlut). Using a genetically encoded calcium indicator (GCaMP8f), we first demonstrate that using artificial cerebrospinal fluid (ACSF) lacking Mg2+ (Mg2+-free) significantly increases neuronal firing, and that firing is enhanced by a potentiator (glycine) but inhibited by the NMDA-R antagonist AP-V. Similarly, multi-electrode array (MEA) recordings also show robust firing in Mg2+-free ACSF. Lastly, single-cell patch-clamp electrophysiology confirms the high firing rates in Mg2+-free ACSF across multiple iPSC donor lines and also reveals iPSC donor-specific tonic and bursting firing phenotypes. This new methodology provides a scalable, high-throughput method to study neuronal activity in iGlut neurons while preserving single-cell resolution. The strategy also reveals different functional phenotypes, enabling detailed characterization of iGlut neurons in diverse applications such as CNS disease modeling and drug screening. These findings establish a versatile framework for future studies of neuronal network dynamics and individual excitability in iPSC-derived neuronal cultures.