Purchase this article with an account.
Prahatha Venkatraman, Robert Carmer, Chi Pui Pang, Mingzhi Zhang, Yuk Fai Leung; Understanding the contribution of photoreceptors to the Visual Motor Response. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):998.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Visual Motor Response (VMR) is a startle response that can be observed in larval zebrafish when they are presented with varying intensities of light stimuli; and is elicited by the eye. Two components of the VMR: ON and OFF responses, arise due to light or dark stimulus. The ON response consists of only a rapid response phase which is evident in a scale of seconds; whereas the OFF response in addition to the rapid phase, also consists of a sustained response phase which is evident in a scale of minutes. While VMR has been increasingly used to study chemical screening of compounds, the underlying cellular circuitry has not been fully understood. The research reported here has the goal to identify specific contributions of photoreceptors to the VMR.
To study contribution of rods to VMR, the no optokinetic response fw21 (nof) zebrafish mutant lacking functional cones was used. nof and wildtype (WT) larvae were presented with stimuli and tracked using an infrared camera; and the differences in vision mediated behavior were recorded. The locomotor movements were plotted separately for ON (transition from darkness to light) and OFF responses (transition from light to dark). Rods are sensitive in lower light intensities, thus driving scotopic vision. Thus, light stimuli with intensities ranging from 1440 lux to 0.14 lux were presented to the larvae along with dark stimulus.
When presented with a light stimulus of 1440 lux, at 8 dpf, the nof did not show any rapid ON or OFF responses. Instead there was a delayed ON response and only the sustained response phase was observed as the OFF response. On the other hand, when presented with a light stimulus of 0.14 lux, WT larvae did not show ON response but showed a rapid OFF response. Interestingly, at 0.14 lux the ON response of nof was similar to the WT and very unlike the responses at 1440 lux. They also showed a very rapid OFF response.
The VMR of the nof mutants is very different from that of the WT larvae. Since nof larvae lack cone function, their showing of an OFF response under low-light stimulus, indicates that rods may contribute to the VMR.
This PDF is available to Subscribers Only