Dendritic morphology and its effects on the amplitude and rise-time of synaptic signals in hippocampal CA3 pyramidal cells

Darrell A. Henze, William Cameron, German Barrionuevo

Research output: Contribution to journalArticle

59 Scopus citations

Abstract

Detailed anatomical analysis and compartmental modeling techniques were used to study the impact of CA3b pyramidal cell dendritic morphology and hippocampal anatomy on the amplitude and time course of dendritic synaptic signals. We have used computer-aided tracing methods to obtain accurate three-dimensional representations of 8 CA3b pyramidal cells. The average total dendritic length was 6,332 ± 1,029 μm and 5,062 ± 1,397 μm for the apical and basilar arbors, respectively. These cells also exhibited a rough symmetry in their maximal transverse and septotemporal extents (311 ± 84 μm and 269 ± 106 μm). From the calculated volume of influence (the volume of the neuropil from which the dendritic structures can receive input), it was found that these cells show a limited symmetry between their proximal apical and basilar dendrites (2.1 ± 1.2 x 106 μm3 and 3.5 ± 1.1 x 106 μm3, respectively). Based upon these data, we propose that the geometry of these cells can be approximated by a combination of two cones for the apical arbor and a single cone for the basilar arbor. The reconstructed cells were used to build compartmental models and investigate the extent to which the cellular anatomy determines the efficiency with which dendritic synaptic signals are transferred to the soma. We found that slow, long lasting signals show only approximately a 50% attenuation when they occur in the most distal apical dendrites. However, synaptic transients similar to those seen in fast glutamatergic transmission are transferred much less efficiently, showing up to a 95% attenuation. The relationship between the distance along the dendrites and the observed attenuation for a transient is described simply by single exponential functions with parameters of 195 and 147 μm for the apical and basilar arbors respectively. In contrast, there is no simple relation that describes how a transient is attenuated with respect to these cells' stratified inputs. This lack of a simple relationship arises from the radial orientation of the proximal apical and basilar dendrites. When combined, the anatomical and modeling data suggest that a CA3b cell can be approximated in three dimensions as the combination of three cones. The amplitude and time-course for a synaptic transient can then be predicted using two simple equations.

Original languageEnglish (US)
Pages (from-to)331-344
Number of pages14
JournalJournal of Comparative Neurology
Volume369
Issue number3
DOIs
Publication statusPublished - 1996

    Fingerprint

Keywords

  • afferent input
  • compartmental model
  • dendrites
  • passive neuron
  • synaptic kinetics

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this