title: The interdependence and independence of amacrine cell dendrites: patch-clamp recordings and simulation studies on cultured GABAergic amacrine cells.
abstract: Previously we reported that cultured rat GABAergic amacrine cells can evoke subthreshold graded depolarization and action potentials. Both types of electrical signals are thought to contribute to neurotransmitter release from their dendrites, because Ca(2+) channels in amacrine cells can be activated at a subthreshold level (around -50 mV). The aim of the present study is to describe the spatiotemporal pattern of the spread of these electrical signals in an amacrine cell, using a computer simulation study. The simulation is based on physiological data, obtained by dual whole-cell patch-clamp recordings on the soma and the dendrites of cultured rat GABAergic amacrine cells. We determined passive and active properties of amacrine cells from the physiological recordings. Then, using the NEURON simulator, we conducted computer simulations on a reconstructed model of amacrine cells. We show that graded potentials and action potentials spread through amacrine cells with distinct patterns, and discuss the electrical interrelationship among the dendrites of an amacrine cell. Subthreshold graded potentials applied to a distal dendrite were sufficiently localized, so that each dendrite could behave independently (dendritic independence). However, at a suprathreshold level, once action potentials were triggered, they propagated into every dendrite, exciting the entire cell (dendritic interdependence). We also showed that GABAergic inhibitory inputs on the dendrites suppress the dendritic interdependence of amacrine cells. These results suggest that an inhibitory amacrine cell can mediate both local and wide-field lateral inhibition, regulated by the spatiotemporal pattern of excitatory and inhibitory synaptic inputs on its dendrites.
authors.affiliation: Keio University School of Medicine, Department of Physiology, Shinjuku, Tokyo, Japan. akoizumi-ns@umin.ac.jp
authors.forename: Amane
authors.initials: A
authors.lastname: Koizumi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hayashida
authors.forename: Teppei
authors.initials: T
authors.lastname: Kiuchi
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Yamada
authors.forename: Atsunori
authors.initials: A
authors.lastname: Fujii
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yagi
authors.forename: Akimichi
authors.initials: A
authors.lastname: Kaneko
mesh_terms: D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D025042:Amacrine Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003198:Computer Simulation; D003712:Dendrites / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D008959:Models, Neurological; D009431:Neural Conduction / Q000187:drug effects / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D012160:Retina / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D005680:gamma-Aminobutyric Acid