Afterpotential characteristics and firing patterns in maturing rat hippocampal CA1 neurones in in vitro slices

Abstract

The postnatal evolution of depolarizing after-potentials (DAPs) and after-hyperpolarizations (AHPs) was studied in rat CA1 hippocampal neurones (5–68 days of age) using in vitro slices. Results were pooled into 4 age groups: P 5–9, P 10–16, P 17–24 and P 26–68. In P 5–9 cells. DAPs were seen as passive signals, with a time constant similar to the time constant of the membrane. The evolution of the DAP was characterized by a decrease in amplitude, an increase in duration and a change in contour. In P 10–16 and P 17–24 cells, the DAPs often had a plateau or a hump-like shape which increased the probability of firing and the occurrence of spike doublets. The firing pattern and bursting behaviour of P 10–16 CA1 neurones differed from the pattern typical of the adult. P 5–9 and P 10–16 cells had post-burst AHPs with a smaller amplitude and a more prolonged early phase than at late stages of development.