The effect of different morphological sampling criteria on the fraction of bursting cells recorded in the rat subiculum in vitro.

In spite of the large variability of the fraction of bursting cells reported in the subiculum (from 54 to 100%), this structure has been considered as intrinsically bursting. Here, using visually assisted whole-cell recordings and Neurobiotin labeling in vitro, we correlated the electrophysiological firing modes of subicular cells (bursting, regular-spiking and fast-spiking) with their morphological characteristics (somatic size and shape). We then examined how different morphological sampling criteria for patching affect cell classification. We found a dramatic variability in the fraction of bursting cells, which ranged from 30 to 76% depending on the sampling criteria. We discuss the implications of these findings for the notion of the subiculum as an intrinsically bursting structure.