Diversity of Axonal and Dendritic Contributions to Neuronal Output

Abstract

Our general understanding of neuronal function is that dendrites receive information that is transmitted to the axon, where action potentials (APs) are initiated and propagated to eventually trigger neurotransmitter release at synaptic terminals. Even though this canonical division of labor is true for a number of neuronal types in the mammalian brain (including neocortical and hippocampal pyramidal neurons or cerebellar Purkinje neurons), many neuronal types do not comply with this classical polarity scheme. In fact, dendrites can be the site of AP initiation and propagation, and even neurotransmitter release. In several interneuron types, all functions are carried out by dendrites as these neurons are devoid of a canonical axon. In this article, we present a few examples of "misbehaving" neurons (with a non-canonical polarity scheme) to highlight the diversity of solutions that are used by mammalian neurons to transmit information. Moreover, we discuss how the contribution of dendrites and axons to neuronal excitability may impose constraints on the morphology of these compartments in specific functional contexts.

Distinctive Properties and Powerful Neuromodulation of Nav1.6 Sodium Channels Regulates Neuronal Excitability

“…Although expression of Na v 1.6 at the AIS and nodes is crucial for the initiation and propagation of signals down the axon, its expression within dendritic compartments also impacts synaptic transmission. Nav currents have been detected in numerous hippocampal and neocortical dendrites where they function to integrate synaptic inputs and contribute to local dendritic spike generation [ 67 , 68 , 69 , 70 ]. Patch-clamp experiments have also demonstrated that the axonal and dendritic Nav currents differ in their biophysical properties [ 71 , 72 ], which might suggest different Nav isoform expression at these subcellular compartments.…”

A multi-modal fitting approach to construct single-neuron models with patch clamp and high-density microelectrode arrays

“…For this reason, when reconstructing the morphology, we did not differentiate between apical and basal dendrite and we applied the same mechanisms to all dendritic sections. Moreover, for both cells the AIS did not originate directly from the soma but from one of the dendrites, which is termed an axon-bearing dendrite (ABD) [67, 30]. Despite these differences, we used the same mechanisms of the ground-truth model detailed in the previous sections and considered the ABD as a “normal” dendrite section (see Methods - Experimental data analysis for details).…”

The regulatory landscape of neurite development in Caenorhabditis elegans

“…Neurites are neuronal projections that transmit information within the nervous system and to non-neuronal cells and tissues ( Cook et al, 2019 ). Neurites are classified as axons and dendrites that transfer information from and to the cell body (soma), respectively ( Goaillard et al, 2019 ). In most vertebrates, axons are insulated by a protective myelin sheath that enables rapid electrical conductance, whereas some animals such as C. elegans lack such structures ( Oikonomou and Shaham, 2011 ).…”