More than a century ago, Santiago Ramon y Cajal provided us with a tremendously extensive description of the various morphologies of the neuronal types constituting the mammalian brain and other speciesвЂ™ nervous systems ( Cajal, 1952). 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. In this article, we present a few examples of вЂњmisbehavingвЂќ neurons (with a non-canonical polarity scheme) to highlight the diversity of solutions that are used by mammalian neurons to transmit information. In several interneuron types, all functions are carried out by dendrites as these neurons are devoid of a canonical axon. In fact, dendrites can be the site of AP initiation and propagation, and even neurotransmitter release. 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. 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. UMR_S 1072, Aix Marseille UniversitГ©, INSERM, FacultГ© de MГ©decine Secteur Nord, Marseille, France.

Jean-Marc Goaillard *вЂ , Estelle Moubarak вЂ , MГіnica Tapia and Fabien Tell

Axon vs dendrite