Off Anatomical Alpha/Physiological Y Ganglion

References The Alpha classification is largely an anatomical distinction for a cat ganglion cell but it is strongly linked to the physiologically classified Y cat ganglion cell. Alpha cells form "3-4% of the ganglion cell population across the whole retina" Kolb and Nelson (1993).

• Postsynaptic connections (Input)
  • Bipolar Cell
    • @ 9 degrees: 258 bipolar synapses
    • @ 1 degree: 434 bipolar synapses
  • Amacrine Cell

    Input Synapses Kolb & Nelson '93

    Presynaptic Cell	Synapses	% of Total	Probable # of cells	Syn density /um2
    cb2/CBa1	52	20%	7	.01
    AII	41	16%	10	.01
    Unknown A	158	64%	39	.04
    Total	251	100%	56	.06

  • 5 - 7 Off Alpha Ganglion Cells via electrical synapses Vaney, 1991 cited in Vaney, 1994

• Presynaptic connections (Output)
  • 5 - 7 Off Alpha Ganglion Cells via electrical synapses Vaney, 1991 cited in Vaney, 1994
  • Lateral Geniculate Nucleus

• Function
  • Troy & Robson's '92 gamma distribution function fitted to the Interspike interval histogram of an Off X retinal ganglion cell when it is stimulated by a uniform field.
  • The Off-center Alpha/Y has a lower mean firing rate than the On-center Alpha/Y.
  • Temporal attributes of the spike train during Steady Discharge Troy & Robson (1992):
    • The interspike interval histograms of the steady-state response to a stationary grating are well described by a gamma distribution function of order 2.8 (stdev .84).
    • The approx. range of isi's is from 0 to 650 msec.
    • Mean firing rate for the Off-center Y/Alpha:
      • 5.0 spikes/sec (stdev 5.3) [range ]- Troy & Robson
      • 17 (9.4) - Stone and Fukuda
    • Immediate neighboring ISIs are negatively correlated.
    • Distal neighbor ISIs are slightly positively correlated.
    • The higher the firing rate of an Alpha/X the more negative the correlation between immediately neighboring ISIs.
  • Beta/X axonal conductance velocity is slower than Alpha/Y axonal conductance velocity - Cleland, Dubin and Levick, W. R. (1971) & Stone and Hoffmann '71

• Morphology (Sterling Lab)
  • 1 degree
    • 4506 micrometer2 membrane area,
    • 10 synapses/100 micrometer2
  • 9 degrees
    • 2029 micrometer2 membrane area,
    • 13 synapses/100 micrometer2
  • Bipolar synaptic density is virtually the same for ON alpha and OFF alpha
  • Bipolar synaptic density of Alphas is less than half of that of Betas
  • Kolb and Nelson, 1993: 3.5 mm (~ 11.6 degrees)
    • Dendrites branched in "distal third" or s1 of sublamina a of the IPL
    • Soma: almost 40 um wide
    • Dendritic spread large diameter: 920 um (large, usually 600-700 um)
    • Dendritic spread shorter diameter: 680 um

• Array characteristics
  • "From central to peripheral retina alpha dendritic fields increase about four-fold in diameter (200-800 um), reaching assymptote at about 8mm (Fig. 5A; Figure 7 in Boycott and Wassle, 1974)." Kier, Buchsbaum and Sterling '95
  • -> area = (.0314m2 - .503mm2)

• Compartmental Model Characteristics

• Location

• Subclasses

• Synapse types

• Synapse Receptors

• Neurotransmitters
  • GABA - Systemically applied Picrotoxin (known to block GABA) reduces 2nd harmonic component, but has no effect on the fundamental response. (Frishman & Linsenmeier, 1982 as cited by Enroth-Cugell and Freeman, 1987)
  • Glycine - there is conflicting evidence in regard to the effects of glycine on On- and Off- Alpha/Y cell responses, but it looks like there is a glycinergic input.
    • Glycinergic impact
      • 19% (~719 synapses) onto the On-Alpha/Y Ganglion cell are from glycine-accumulating amacrine cells (postulated as A4). (Freed and Sterling, 1988)
      • Quisquilate and AMPA (which have specialized glutamate receptors) inhibit Off Alpha/Y response. This inhibition could be reduced either by strychnine (or by bicuculline).
    • No Glycinergic impact: Strychnine (an antagonist of glycine) does not affect On- and Off- Alpha/Y cell response. (It does reduce the response of the On- and Off- Beta/X cell response.) - Kirby, 1979
  • Increased spiking at spontaneous and stimulated (Boos, Muller and Wassle, 1990)
    • glutamate (GLU)
    • Asparate (ASP)
    • Kainate (KA) - more effective than ASP and GLU at lower concentrations (more effective on X-cells than Y-cells)
    • Quisqualate (QQ) and AMPA - looks like (directly or indirectly) QQ excites, but it also appears to excite inhibitory neurons presynaptic to the ganglion cells
    • NMDA excites
  • "GABAergic and glycinergic transmission seem to have a different time course; during application of bicuculline (blocks GABA) the transient excitatory component at the beginning of QQ-application was chiefly enhanced, whereas during application of strychnine (blocks glycine), QQ had an excitatory action during its entire ejection time." (Boos, Muller and Wassle, 1990)

• Immunoreactivity

• Nomenclature
  • The Alpha classification is largely an anatomical distinction for a cat ganglion cell. It is commonly linked with the physiologically classified Y cat ganglion cell (Enroth-Cugell and Robson, 1966; Peichl and Wassle, 1983;Saito, 1983; Fukuda et al, 1984; Stanford and Sherman, 1984)
  • X-type and Y-type have also been refered to as brisk (firing) cells or brisk-sustained and brisk-transient. (i.e. Bolz, Wassle and Thier, 1984).
  • Class I - i.e. Berson, Pu and Famiglietti '96 ARVO

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