Heterogeneity of neuronal firing type and morphology in retrosplenial cortex of male F344 rats

This is the first study to demonstrate that granular retrosplenial cortical (gRSC) neurons exhibit five distinctive firing types: regular spiking (RS), regular spiking with an afterdepolarization (RS ADP ), late spiking (LS), burst spiking (BS), and fast spiking (FS). RS ADP neurons were the most frequently observed cell type in adult gRSC neurons. Interestingly, RS neurons without an ADP were most common in gRSC neurons of juvenile rats (PND 14–30). Thus, the ADP property, which was previously shown to enhance neuronal excitability, emerges during development.