Abstract
Abstract: :
Purpose: The use of pharmacological agents to selectively suppress the ON- and OFF-pathways has provided valuable information about visual processing. For example, intravitreal injection of DL-2-amino-4-phosphonobutyric acid (APB), which suppresses the responses of the ON-pathway, reduces goldfish behavioral visual acuity. The purpose of this study was to determine whether suppressing the ON- and OFF-pathways in larvae zebrafish alters visual behavior. Pathway suppression was accomplished by exposing subjects to either APB or cis-2,3-piperidinedicarboxylic acid (PDA). APB has been shown to suppress the responses of the ON-pathway; PDA has been shown to suppress the OFF-pathway response. Visual behavior was assessed with the optomotor response. Methods: Larvae (6-8 days postfertilization) zebrafish (Danio rerio) were submerged into either a 0.25 mM solution of APB, PDA, or tank water (control). Visual behavior was examined using the optomotor response to black and white vertical rotating stripes of seven spatial frequencies. The stripe width at which the subject no longer follows the stripe movement is its visual acuity limit. Baseline responses were obtained at the beginning and the end of the test session to ensure that there were no detrimental drug effects other than on visual responses. Results: All three groups were similar in response to low spatial frequency stimuli. However, subjects exposed to either APB or PDA had significantly lower responses to middle and high spatial frequency stimuli than did the control group, suggesting that both drug groups had lower visual acuity than did the control group. Conclusions: Both APB and PDA affect the visual behavior of larvae zebrafish by lowering visual acuity. Results indicate that both the ON- and OFF-pathways are necessary for normal visual behavior, consistent with results from other species. These results also illustrate the usefulness of this behavioral method in evaluating the effects of pharmacological agents on larvae zebrafish.
Keywords: spatial vision • drug toxicity/drug effects • visual acuity