Axonal conduction velocities of functionally characterized retinal ganglion cells in goldfish

Abstract

Visual response properties and conduction velocities of retinal ganglion cells were studied by extracellular recordings in the intact goldfish eye. Visually responsive single units were confirmed as ganglion cells by collision testing, and their receptive fields were mapped. From compound action potentials, we identified groups I‐V in the optic nerve, with overall conduction velocities of 11.5 ± 1.17, 7.1 ± 0.79, 4.4 ± 0.56, 3.1 ± 0.31 and 2.3 ± 0.18 m s−1 (mean ± s.d.) at 23 °C. Ganglion cells were classified by their receptive fields as off‐, on‐off‐ or on‐centre. Nearly all confirmed ganglion cells had axonal conduction velocities in groups II, III and IV; none fell in the fastest group, I. Off‐centre ganglion cells had conduction velocities only in the fast group, II. On‐off‐centre cells fell mainly in group III, with some in group II. On‐centre cells fell in groups II‐V, but mainly in groups III and IV. Receptive field centre diameters were 5‐30 deg measured with a photopic background. The mean diameters for off‐, on‐off‐ and on‐centres were 24, 15 and 18 deg, respectively. The relatively larger diameter and higher rate of spontaneous firing of the off‐centre cells were maintained under different adaptation conditions. The off‐centre cells can be identified with an anatomical class of large, α‐like ganglion cells in the goldfish retina.

Heterogeneous Intrinsic Firing Properties of Vertebrate Retinal Ganglion Cells

“…Goldfish RGCs are classified into ON and OFF subtypes, which display relatively sustained responses to stepped illumination of a particular wavelength (typically red), and the ON-OFF subtype, which displays a relatively transient response (see, e.g., Spekreijse et al 1972). An intracellular recording/staining study (Vallerga and Djamgoz 1991) and an axonal conduction velocity measurement (Northmore and Oh 1998) suggested that OFF goldfish RGCs correspond to a morphological subtype with the largest somata Hitchcock and Easter 1986). A few tonic RGCs with exceptionally large somata (Fig.…”

“…These RGCs might also overlap Y-like RGCs to a large extent because OFF RGCs often are identified as Y-like RGCs (Bilotta and Abramov 1989). Moreover, the velocity measurement (Northmore and Oh 1998) suggests that the ON subtype contains more small RGCs than does the ON-OFF subtype. With respect to relative soma size ( Fig.…”

Functional properties of retinal ganglion cells during optic nerve regeneration in the goldfish

“…Since OFF and ON responses recover at different times, it is important to know how the activity of different functional classes of ganglion cell change over time. We therefore extended the study of single-cell recordings of normal ganglion cells (Northmore & Oh, 1998) to ganglion cells subjected to axotomy by section of the optic tract. The results reveal a sequential program played out by the different types of ganglion cells as they reestablish ordered connections in the brain.…”

Estudio Morfométrico del Nervio Óptico de Tiburoncito (Ariopsis seemanni)

“…En términos de velocidad de conducción, se ha seña-lado que, en general, la mayoría de las fibras del nervio óp-tico tienen en promedio velocidades de conducción bajas, entre 2.2 a 5.1 m/s2 (Northmore & Oh, 1998;Bakken & Stevens 2011). Adicionalmente, la literatura plantea que el nervio óptico tiene pocas fibras con mayor velocidad de conducción y que, probablemente, están asociadas con fibras eferentes que conducen señales del cerebro hacia la retina, puesto que se ha descrito que en teleósteos estas fibras retinopetales tienen tamaños del orden de 1-3 µm (Northmore & Oh 1998;Reperand et al, 2006).…”

“…Adicionalmente, la literatura plantea que el nervio óptico tiene pocas fibras con mayor velocidad de conducción y que, probablemente, están asociadas con fibras eferentes que conducen señales del cerebro hacia la retina, puesto que se ha descrito que en teleósteos estas fibras retinopetales tienen tamaños del orden de 1-3 µm (Northmore & Oh 1998;Reperand et al, 2006). Diversos autores (apud Reperand et al, 2006) sugieren que estas fibras pueden provenir del sistema olfatorio y modular la sensibilidad al contraste de colores, o que también que corresponden a fibras que llevan impulsos táctiles.…”