Active dendrites and spike propagation in multicompartment models of oriens‐lacunosum/moleculare hippocampal interneurons

Abstract

It is well known that interneurons are heterogeneous in their morphologies, biophysical properties, pharmacological sensitivities and electrophysiological responses, but it is unknown how best to understand this diversity. Given their critical roles in shaping brain output, it is important to try to understand the functionality of their computational characteristics. To do this, we focus on specific interneuron subtypes. In particular, it has recently been shown that long‐term potentiation is induced specifically on oriens‐lacunosum/moleculare (O‐LM) interneurons in hippocampus CA1 and that the same cells contain the highest density of dendritic sodium and potassium conductances measured to date. We have created multi‐compartment models of an O‐LM hippocampal interneuron using passive properties, channel kinetics, densities and distributions specific to this cell type, and explored its signalling characteristics. We found that spike initiation depends on both location and amount of input, as well as the intrinsic properties of the interneuron. Distal synaptic input always produces strong back‐propagating spikes whereas proximal input could produce both forward‐ and back‐propagating spikes depending on the input strength. We speculate that the highly active dendrites of these interneurons endow them with a specialized function within the hippocampal circuitry by allowing them to regulate direct and indirect signalling pathways within the hippocampus.

Branch-Specific Ca2+Influx from Na+-Dependent Dendritic Spikes in Olfactory Granule Cells

“…The extent to which Na ϩ -dependent action potentials (APs) backpropagate into or are initiated in dendrites (Bischofberger and Jonas, 1997;Chen et al, 1997;Saraga et al, 2003) varies across neuronal types and often depends on factors such as resting membrane potential, spiking pattern (Hoffman et al, 1997), synaptic activity (Margrie et al, 2001;Lowe, 2002), or neuromodulation (Tsubokawa and Ross, 1997;Hoffman and Johnston, 1999;Davison et al, 2004).…”

Distinct nonuniform cable properties optimize rapid and efficient activation of fast-spiking GABAergic interneurons

“…Furthermore, the axonal arborization was not included in any of these studies, and a possible nonuniformity of R m was not considered (27, 28). However, complete passive cable models will be necessary for understanding the mechanisms of both dendritic integration and action potential initiation in GABAergic interneurons (13,29).To address these questions, we developed detailed passive cable models (27,28,(30)(31)(32) of BCs in the dentate gyrus. To obtain accurate measurement of R i and somatodendritic nonuniformity of R m , both dual somatic and somatodendritic recordings were performed.…”

“…Furthermore, the axonal arborization was not included in any of these studies, and a possible nonuniformity of R m was not considered (27, 28). However, complete passive cable models will be necessary for understanding the mechanisms of both dendritic integration and action potential initiation in GABAergic interneurons (13,29).…”

Neurotech for Neuroscience: Unifying Concepts, Organizing Principles, and Emerging Tools

“…In contrast, the theta rhythm can be produced by individual cells (Klink and Alonso, 1993;Dickson et al, 2000;Saraga et al, 2003), although a coherent population rhythm depends on connectivity (Netoff et al, 2005;Rotstein et al, 2006). In all cases, the rhythm depends on intrinsic currents that do not seem to be important for the gamma rhythm.…”

“…In all cases, the rhythm depends on intrinsic currents that do not seem to be important for the gamma rhythm. These include the hyperpolarization-activated h-current, the persistent sodium current, and the M-current and/or the A-current (Klink and Alonso, 1997;Acker et al, 2003;Saraga et al, 2003).…”