Different erg (ether-à-go-go-related gene) K channel subunits are expressed throughout the mouse brain, and especially the mitral cell layer of the olfactory bulb is stained intensely by erg1a, erg1b, erg2 and erg3 antibodies (Guasti et al. J Comp Neurol 2005). We have now characterized the erg current in mitral/tufted cells (M/T) from the olfactory bulb of neonatal mice in primary culture. The erg current was isolated with the help of the selective erg channel blocker E-4031. Single-cell RT-PCR revealed the expression of erg1a, erg1b and erg3 mRNA in M/T cells, and Western blot analysis indicated the presence of erg1a, b and only weak erg2 expression. Despite a similar erg subunit expression pattern in M/T cells and embryonal rat raphe neurons (Hirdes et al. J Physiol 2005), the two neuronal erg currents have distinct properties. The M/T erg current exhibited considerably slower deactivation kinetics and it activated at about 10 mV more negative potentials. As observed in the raphe neurons, pharmacological block of the erg channels had only marginal effects on the membrane potential of M/T cells. Thus, the physiological significance of the numerous erg channels in the central nervous system remains to be unravelled. Supported by SFB 444, A3