Nanometer-scale dendritic shaft constrictions shape dendritic integration and plasticity

Tony Kelly¹, Michela Barboni², Michael Döngi², Juan Eduardo Rodriguez-Gatica², Carlos Wert-Carvajal², Philipp Bethge³, Michel Herde², Jens Tillmann², Sebastian Dupraz⁴, Frank Bradke⁴, Martin Schwarz², Ulrich Kubitscheck², Valentin Nägerl³, Tatjana Tchumatchenko², Heinz Beck²

¹ IEECR, University Bonn
² University Bonn
³ Université de Bordeaux
⁴ DZNE

Dendrites are the main input structures of neurons and compartmentalisation is a key feature, with the intricate structure of spine necks creating single synapse compartments. However, the morphological features compartmentalising along single branches are less well understood. Employing super-resolution techniques and electron microscopy, we identified localized reductions in dendritic shaft diameter to <300nm, termed dendritic shaft constrictions (DSCs). DSCs occurred primarily in distal dendrites, creating sub-compartments. Computational modelling and experimental glutamate uncaging revealed rapid saturation of synaptic signals and NMDA receptor recruitment in distal compartments. Gamma-patterned distal inputs induced NMDA-mediated plateau potentials, eliciting prolonged Ca²⁺ transients at the distal input site, and Ca²⁺ transients mediated by intracellular released at the proximal site. The distal plateau potentials lead to cooperative branch-specific potentiation of proximal inputs and enhances information storage in dendrites. Taken together, DSCs establish high impedance compartments favoring NMDA plateau potentials, with distal-induced potentials gating proximal plasticity through Ca²⁺ release.