Fig. 2.

Effects of norepinephrine (NE) modulation on cellular parameters. A: NE modulates Gr cell spontaneous firing (Nai et al. 2010). The measured effects of NE activation of α1- and α2-receptors on Gr cell-mediated spontaneous inhibitory postsynaptic currents (IPSCs) was simulated by changes in Gr cell firing thresholds [in abstract parameters; equations described in detail by Escanilla et al. (2010)]. α1- and α2-receptor activation modulate spontaneous IPSCs in opposite directions, each with their own concentration dependency. The summated effect is a nonmonotonic modulation of firing threshold. B: effect of threshold modulation on Gr cell spontaneous firing. The size of the effect was adjusted to data reported by Ennis and colleagues (Nai et al. 2009, 2010). C: modulation of membrane potential by NE in model Mi cells. The size of the effect was modeled after data reported by Hayar et al. (2001). In the model, spontaneous activity was not effected by this effect, but responses to low-threshold stimuli were modulated. D: modulation of response probability to low-threshold stimuli in Mi cells. Both modulation of inhibition by α2 and α2 effects on Gr cell firing and direct modulation of Mi cell membrane potential were taken into account. Mi cell responses to low-amplitude stimuli were modulated in a nonmonotonic manner by simulated NE due to the additive effects of NE receptor activation.