Here we recorded the growth properties of dendrites in culture from 14 to 42 days in vitro. In general, dendrites are much shorter and thicker than axons and have a tapered appearance. First, we wanted to determine the percentage of microgrooves that possessed dendrites. Although variable and largely dependent on cell plating density, at least 50% of the microgrooves contained dendrites greater than 100 μm in length after 14 days. There was no change in the number of dendrite-filled microgrooves with culture age, indicating that after 14 days in culture the location of the dendrites is well established. Second, we measured the length of dendrites within each chamber for all culture ages and plotted their distribution (Figure 1C). At 14 days in culture, the average dendritic length was 165 μm and at 21 days the average length extended to 214 μm. At longer culture ages, the dendrites did not extend further into the microgrooves, indicating that absolute dendritic growth within the microfluidic chamber slows or stops after 21 days; notably, however, the length did not decrease.
