Model-based study on activeness of neuronal dendrites and its functional significance

Recent neurophysiological experiments showed that neuronal dendrites could be recognized as active systems rather than passive transmission lines due to the existence of varied types of voltage-gated ionic channels. This study is performed to clarify functional significance of such an active propery of neuronal dendrites. In order to achieve this, a compartment neuron modal is constructed so that the model closely mimicks the most recently found responsiveness of neurons with active dendrites. Based on the model, generation and propagation of action potentials and the associated behavior of intracellular Ca²⁺ concentration are simulated for various combinations of synaptic inputs. Inhibitory synaptic inputs are found to control the propagating dendritic area of the action potentials. Since the propagation of the action potential is accompanied by an increase of intracellular Ca²⁺ concentration, the inhibitory input could shape synaptic organizations on the dendritic tree through the well-known Ca²⁺-induced synaptic plastihity. In addition, an action potential generation in the soma is shown to differentiate levels of the interacellular Ca²⁺ concentration in the whole dendritic area. Finally, we reach the hypothesis that the activeness of the dendritic system could serve to broadcast the information concerning somatic firing to the whole dendritic tree, which is mediated by the associated increase of the intracellular Ca²⁺ concentration.