Differences in biophysical properties of nucleus accumbens medium spiny neurons emerging from inactivation of inward rectifying potassium currents

Modulation of synaptic potentials and cell excitability by dendritic KIR and KAs channels in nucleus accumbens medium spiny neurons: A computational study

“…Figure 8B summarizes this data showing that number of spikes increased with reduction in g max (K IR ). Table 3 shows that the latency to the first spike increased with g max (K IR ), thus indicating that K IR conductance acts to increase the duration of the depolarizing ramp before firing the action potential, as also suggested by previous computational studies ( Moyer et al 2007;Steephen and Manchanda 2009).…”

“…In this study, data from published models (Wolf et al 2005;Steephen and Manchanda 2009) were used to build a 189-compartment stylized model of the NAc MS neuron using the NEURON simulation platform (Carnevale and Hines 2006). The radially symmetric model included a soma and 4 proximal dendrites, each of which bifurcate twice to form 8 middle dendrites and 16 distal dendrites (figure 1A).…”

“…The parameters, except for the time constant of activation of K IR channels, for modelling the different channels were taken directly from Wolf et al (2005). These parameters were obtained from a recent computational study (Steephen and Manchanda 2009), in which the values were derived from rat neurons instead of the non-mammalian aplysia neurons as in Wolf et al (2005). Hodgkin-Huxley formulations were used to model the sodium and potassium currents, the level of inactivation in each channel being adjusted using a variable whose value was set to match published data (Wolf et al 2005).…”

“…Out of the 84 GABA-ergic synapses, 16 were placed at the soma, 3 in each of the primary and middle dendrites and 2 in each of the distal dendrites. The procedure for applying temporally dispersed, random inputs to the spatially distributed synapses was adopted from literature (Steephen and Manchanda 2009). Each of the excitatory or inhibitory synapses received an independent, probabilistic spike train that was generated with NEURON using the following algorithm.…”

“…These studies indicated that K IR plays a dominant role in modulating the electrical behaviour of the neuron in the down-state. However, as indicated earlier, as recent studies have shown that striatal neurons possess a wide range of nonlinear active channels and a biophysically more detailed model of the neuron incorporating all these channels is currently available in the literature (Wolf et al 2005, Steephen andManchanda 2009), we wished to investigate in detail (i) whether K IR conductance continues to play a dominant role in the downstate even in the presence of the other non-linear active conductances in the neuron and (ii) whether any of the other channels plays a role in modulating the EPSPs in NAc MS neurons in the down-state as well as in the depolarized membrane potentials of the neuron. We find that, in the down-state, while the contribution from most channels is absent or negligibly small, dendritic K IR channels do contribute significantly to this modulation even in the presence of other active conductances.…”