Form and function of ON-OFF amacrine cells in the amphibian retina.
ON-OFF amacrine cells were studied with whole cell recording techniques and intracellular staining methods using intact retina-eyecup preparations of the tiger salamander (Ambystoma tigrinum) and the mudpuppy (Necturus maculosus). Morphological characterization of these cells included three-dimensional reconstruction methods based on serial optical sections obtained with a confocal microscope. Some cells had their detailed morphology digitized with a computer-assisted tracing system and converted to compartmental models for computer simulations. The dendrites of ON-OFF amacrine cells have spines and numerous varicosities. Physiological recordings confirmed that ON-OFF amacrine cells generate both large- and small-amplitude impulses attributed, respectively, to somatic and dendritic generation sites. Using a multichannel model for impulse generation, computer simulations were carried out to evaluate how impulses are likely to propagate throughout these structures. We conclude that the ON-OFF amacrine cell is organized with multifocal dendritic impulse generating sites and that both dendritic and somatic impulse activity contribute to the functional repertoire of these interneurons: locally generated dendritic impulses can provide regional activation, while somatic impulse activity results in rapid activation of the entire dendritic tree.
Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455, USA. rfm@umn.edu
Robert F
RF
Miller
Nathan P
NP
Staff
Toby J
TJ
Velte
D025042:Amacrine Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D000663:Amphibians / Q000502:physiology*; D000818:Animals; D049229:Dendritic Spines; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D021621:Imaging, Three-Dimensional / Q000379:methods; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D008959:Models, Neurological; D009431:Neural Conduction / Q000502:physiology / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000166:cytology*; D013997:Time Factors
D005456:Fluorescent Dyes