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Figure 1. Protocol for Plating and Culturing Primary Neurons with the SM1 Culture System

Primary rodent tissue dissociated in papain was plated in NeuroCult? Neuronal Plating Medium, supplemented with NeuroCult? SM1 Neuronal Supplement, L-Glutamine, and L-Glutamic Acid. On day 5, primary neurons were transitioned to BrainPhys? Neuronal Medium, supplemented with NeuroCult? SM1 Neuronal Supplement, by performing half-medium changes every 3 - 4 days.

Figure 2. The SM1 Culture System Supports Long-Term Culture of Rodent Neurons

Primary E18 rat cortical neurons were cultured in the SM1 Culture System. A large number of viable neurons are visible after (A) 21 and (B) 35 days, as demonstrated by their bright neuronal cell bodies, and extensive neurite outgrowth and branching. Neurons are evenly distributed over the culture surface with minimal cell clumping.

Figure 3. Pre- and Post-Synaptic Markers are Expressed in Rodent Neurons Cultured in the SM1 Culture System

Primary E18 rat cortical neurons were cultured in the SM1 Culture System. At 21 DIV, neurons are phenotypically mature, as indicated by the presence of an extensive dendritic arbor, and appropriate expression and localization of pre-synaptic synapsin (A,C; green) and post-synaptic PSD-95 (A,B; red) markers. Synapsin is concentrated in discrete puncta distributed along the somata and dendritic processes, as defined by the dendritic marker MAP2 (A,D; blue).

Figure 4. Glucose Supplementation in BrainPhys? Maintains Neuronal Activity Over 8 Weeks in Culture

Primary E18 rat cortical neurons were cultured with BrainPhys? and SM1 or other commercially available culture systems for 8 weeks. Neuronal activity can be detected at Day 9 with BrainPhys?, whereas activity is not detected until Day 14 in cultures maintained in either of the Commercial Media with Commercial Supplements. For Commercial Medium and Supplement-cultured neurons, mean firing rate remains low throughout culture. In contrast, a ¡°peak-drop¡± activity pattern is observed in the Commercial Medium Plus condition, where mean firing rate increases rapidly within 2 days, followed by a drop in activity in the next 2 - 4 days. BrainPhys?and SM1 Kit with 15 mM glucose maintains the highest level of activity throughout the 8-week culture period.

Figure 5. BrainPhys? Supports Improved Neuronal Activity and More Consistent Network Bursting in Long-Term Culture

Raster plots from MEA recordings show the firing patterns of neurons across 8 electrodes at Weeks 2, 4, 6 and 8. Neurons were either cultured with a Commercial Medium with Supplements, Commercial Medium Plus with Supplements, BrainPhys? and SM1, or BrainPhys? and SM1 with 15 mM glucose. Detected spikes (black lines), single channel bursts (blue lines; a collection of at least 5 spikes, each separated by an ISI of no more than 100 ms), and network bursts (magenta boxes; a collection of at least 50 spikes from a minimum of 35% of participating electrodes across each well, each separated by an ISI of no more than 100 ms) were recorded for each medium. (A-D) Neurons cultured with Commercial Medium exhibited network bursting in Week 2 but no spiking activity was detected in subsequent timepoints. (E-H) In Commercial Medium Plus-cultured neurons, a high number of spikes and regular network bursting were detected at Week 2. A decreased number of spikes and inconsistent network bursting were observed in later time points, corresponding to the drop in MFR seen in Figure 4. (I-L) Without glucose, individual spiking was observed at Weeks 2 and 4 with BrainPhys? and SM1 but network bursting was not detected until Weeks 6 and 8. (M-T) In contrast, neurons cultured with BrainPhys? and SM1 with 15 mM glucose demonstrated strong spiking activity and consistent network bursting at all timepoints. MEA = microelectrode array; ISI = inter-spike interval; MFR = mean firing rate