Post-natal development of burst firing behavior and the low-threshold transient calcium current examined using freshly isolated neurons from rat dorsal root ganglia.

Burst firing was triggered by an afterdepolarizing potential (ADP) in whole-cell recordings from neurons recently isolated from dorsal root ganglia (DRG) of adult rats, less frequently in neurons from 12-day-old rats, and not at all in neurons from 1-day-old rats. Both the ADP and voltage-activated transient (T-type) Ca2+ current which generates the ADP were present in neurons at all postnatal ages; however, the amplitude of the ADP and of the T-type current were greatest in neurons from adults, smaller in neurons from 12-day animals, and smallest in neurons from 1-day animals. These observations suggest that the increase in amplitude of the T-type current with age leads to the generation of an ADP of increased amplitude and those properties of the ADP which develop with age may contribute to or generate burst firing behavior.