Multiple mechanisms underlie burst firing in rat midbrain dopamine neurons in vitro.

Both apamin and NMDA evoke burst firing in dopamine neurons recorded intracellularly in slices of rat midbrain. However, apamin-induced bursting required injection of depolarizing currents, and was mimicked by Bay K8644 and blocked by nifedipine. In contrast, NMDA-induced bursting required hyperpolarizing currents and was not blocked by nifedipine. Our results show that burst firing can be evoked in dopamine neurons via two different mechanisms.