(GABAeric) Axon-bearing/PA1 Amacrine Cell

References

Most of this page comes from my notes on Dacey (1989) Axon-Bearing Amacrine Cells of the Macaque Monkey Retina and Famiglietti's '92 papers on Poly-axonal Amacrines in the rabbit.

• Postsynaptic connections (Input)

• Presynaptic connections (Output)

• Function
  • Effect; Similarities to
  • Famigletti '92a: "suggests.... affecting both On and OFF responses, and perhaps On-Off cells selectively" - deduced simply from the stratification along the border between the on and off laminae.

• Morphology
  • Dacey (1989) - 58 HRP filled cells
    • Soma diameter
      • ~15 - 20 um
    • dendritic tree
      • ~40-50 terminal dendrites
      • broadly stratified
      • Dendritic field diameter
        • within 2mm of fovea: ~200 um
        • up to ~500 um in periphery
    • 1-4 axon-like processes
      • roughly concentric
      • 10x larger diameter of dendritic field
      • split ~2 times
      • axons end 1-3mm beyond dendritic tree without much branching
  • Famiglietti (1992a,b)
    • Soma diameter
      • 13 um, 12-15
    • dendritic tree
      • branching angle = 50-90 degrees, but turn towards each other so net angle = 45-70 deg.
      • children branches are smaller than the parent
      • sparsely branched, 7-10 terminal branches
      • non-uniform field coverage
      • many fine spines: "most are .75 to 1 um long, with necks .1 to .2 um in diameter and heads .2 to .4 um in diameter"
      • some larger spines in proximal dendritric tree
      • Dendritic field diameter
        • 400-800 um
        • over 500 um for cells a few mm from visual streak
    • 2-6 axon-like processes
      • axon averages .15 um thick
      • children branches are the same thickness as the parent
      • angle between branching axons = 90-120 degrees
      • one child branch continues as its parent and the second heads off roughly perpendicularlly
      • "The axons give rise to boutons en passant, which occur at irregular intervals and in regions of high frequency at intervals of 8 to 15 um"
      • axon field extend up to and perhaps beyod 2mm from soma
      • "Close apposition has been observed of processes of the latter (narrow-field "bushy" type) with those of PA1 cells. The apparent homolgue of the narrow-field, "bushy" type in cat takes up the neurotransmitter glycine (Pourcho and Goebel,'85)" From reading Pourcho and Goebel, I can tell that Fam is talking about either A3 or A4, I'm pretty sure the A4. There is some debate about whether the A3 and A4 are really different cells or not.
  • Axonal field spans the central 10-20% of the inner plexiform layer.

• Array characteristics
  • Dacey (1989)
    • Periphery
      • intercell spacing +200-300 um
      • 20-25 cells/mm^2
    • coverage factor
      • axon cf = 100 x dendritic cf
  • Famiglietti (1992b)
    • 15-16 cells/mm2 at about 2mm ventral to streak
    • dendritic field overlap = 4x
    • axonal field overlap = 40x

• Compartmental Model Characteristics

• Location
  • Dacey (1989)
    • Dendrites field spans the central 50% of the inner plexiform layer.
    • Somas in the middle of the inner plexiform layer.
    • Axonal field spans the central 10-20% of the inner plexiform layer.
  • Famiglietti (1992a)
    • Dendrites are stratified in sublamina 2 and 3 of the IPL. The greatest concentration of processes is at the a/b sublaminar border. Some processes wander as deep as S4.
    • Within 1.5 mm of the visual streak, the somas were consistently in the middle of the inner plexiform layer, beyond 1.5mm, somas varied widely from the inner margin of the INL through all levels of the IPL to the GCL.
    • Axons are stratified in sublamina 2 and 3 of the IPL.

• Subclasses

• Synapse types

• Synapse Receptors

• Neurotransmitters
  • GABA

• Immunoreactivity
  • Dacey (1989)
    • acride orange stains (but it stains non-specifically)
    • Famiglietti: Golgi-Kpsch-Colonnier method impregnation

• Nomenclature
  • Axon-bearing Amacrine - Dacey '89
  • Famiglietti '92b equates this cell to the rabbit PA1
  • Famiglietti '92a cites a Famiglietti and Siegfried '80 abstract as originally describing the "polyaxonal amacrine cells"
  • Interstitial Amacrine - soma is in the middle of the IPL - Vaney

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