Effects of dopamine on bipolar cell activity in the zebrafish (Danio rerio) retina

<p>Whole cell currents were recorded using patch clamp techniques from zebrafish (Danio rerio) bipolar cells in the in vivo retina slice. Depolarization elicited K+ currents were enhanced 83% above control levels when 200 muM dopamine was present in the recording solution. Enhancement of depolarization elicited K+ currents caused by dopamine was decreased an average 47% by the D1-like receptor antagonist, SCH23390 (5 muM), and an average 30% by the D2-like receptor antagonist, spiperone (10 muM). Affects of D1 and D2 dopamine agonists were also examined. 25 muM SKF-38393, a D1-like receptor agonist, enhanced current amplitude 38%, while 25 muM quinpirole, a D2-like receptor agonist, enhanced depolarization elicited K+ currents 68% above control levels. Co-application of 25 muM SKF-38393 and 25 muM quinpirole only enhanced current amplitude 18%. These findings are significant as they show both D1-like and D2-like dopamine receptors are found in zebrafish bipolar cells, and are often co-localized on the same neurons. Furthermore, the reduced current enhancement following co-application of SKF-38393 and quinpirole is suggestive of an antagonistic interaction between D1 and D2 dopamine receptors.</p>