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Victoria P Connaughton, Ralph F Nelson; Ultraviolet dominates ganglion cell light responses in larval zebrafish retinas. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3251.
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© ARVO (1962-2015); The Authors (2016-present)
To identify, and spectrally classify, light-driven impulse discharges from ganglion cells in larval zebrafish retinas
Ganglion cell (GC) recordings were made using superfused, whole eye preparations from 5-6dpf zebrafish larvae. Eyes were placed cornea-side down in the recording chamber and the electrodes inserted into the optic nerve head. Loose-patch recordings of GC spike discharges were obtained using transcleral stimulation with 9 wavelengths of light (650-330nm), each at 7 light intensities (0.5 ND interval). Post-stimulus time histograms (PSTH) provided qualitative scoring of spectral properties. A spectral model based on the integrated ON discharges isolated the contributing cone inputs.
GCs in 5-6dpf zebrafish retinas have robust spectral responses that readily distinguish stimulus wavelength. All cells responded to 330nm and 370nm stimuli. These UV discharges were large in amplitude and high in sensitivity compared to other wavelengths. UV-sensitive GCs were typically also excited by red (650, 610nm) stimulation. However, most cells did not respond, or responded weakly, to stimulation with 570nm and 490nm light; two wavelengths that correspond to the wavelengths of maximal absorption of zebrafish red and green cone opsins, respectively. Examination of response kinetics identified sustained ON (n = 11/44), transient ON (n = 18/44), and transient ON-OFF type responses (n = 13/44). Transient discharges returned to baseline within the first 300ms of light ON; whereas sustained responses were maintained for more extended durations. Within each of these three categories, diverse spectral subtypes were identified, including the spectrally multiphasic UV responses described above.
GC spectral discriminations in larval zebrafish retinas are well-developed at 5 dpf, the age associated with the onset of exogenous feeding. Responses to UV light stimulation were prominent, indicating retinal circuitry processing UV light stimuli is functional at these ages.
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