Abstract
Abstract: :
Purpose: Motion vision is one of the most important properties of the visual system. As retinal Acetylcholine has been suggested to play a major role in retinal motion coding its influence on motion vision should be investigated in behavioral tasks. The optomotor response (OMR) - a reflex-like behavior of many animals evoked by moving whole field visual stimuli – can be used to measure motion vision. To study the importance of retinal Acetylcholine for motion vision nicotinic and muscarinic receptor antagonists were applied to the retina of goldfish and changes in their OMR recorded. Methods: The OMR is elicited by a rotating (18, 30, 60 and 78 deg/s) pattern cylinder. Goldfish respond by following the rotating pattern and adjusting their swimming velocity to the pattern velocity. The OMR was tested before and after the injection of Curare (intraocular concentrations: 3, 10 or 36 µM) and/or Atropine (10 or 100 µM). Total angular velocities of every fish were determined after the injection of Curare to control for motor effects. Results: Neither the vehicle nor Atropine had any effect on the OMR. Curare reduced the OMR in a concentration-dependent manner: 3 µM had no effect, 10 µM reduced the OMR at 60 and 78 deg/s by up to 50% and 36 µM also reduced the OMR at 18 and 30 deg/s and even eliminated it at 60 and 78 deg/s pattern velocity. Data were excluded once animals exhibited a substantial loss in maximal angular velocity. Two animals received injections of Curare (10 µM) and Atropine (100 µM). The results were similar to the 10 µM Curare injections, i.e. Atropine did not change the Curare induced reduction of the OMR. Conclusions: Acetylcholine seems to be essential for retinal processing of moving whole field stimuli. An effect of Curare on motor activity does not seem to be responsible for the observed loss of the optomotor response. As Atropine was unable to reverse the effect of Curare it is proposed that nicotinic receptors are important for retinal motion processing but muscarinic receptors are not involved.
Keywords: retina • acetylcholine • pharmacology