In vivo Microdialysis and HPLC Detection of Retinal Dopamine Release in Zebrafish

Abstract

Abstract: : Purpose: Retinal dopamine (DA) release has been reported to depend on light conditions. Most studies have investigated this by using in vitro methods. Here we apply in vivo microdialysis and high performance liquid chromatography (HPLC) to elucidate DA release in the zebrafish retina under different light conditions and transitions between them. Methods: A microdialysis probe (CMA7, 1 mm membrane length) was inserted into the eye of zebrafish. Over a period of 90 minutes we collected three vitreal samples for 30 minutes each. Between samples we switched between light conditions (D, dark; L, steady light; F, flickering light, 1 Hz) using the schedules DLD, LDL or DFD. The experiments were carried out between 8:00 and 18:00. Fish were kept under normal cyclic light (room fluorescent light, 8:00 – 22:00). The DA content of the samples was analyzed by means of HPLC with electrochemical detection. Results: Baseline DA release after 30 minutes dark adaptation was the same as after 30 minutes light adaptation. No effect of time of the day was observed. When switching from D to F, DA release increased by 31%. This effect had the tendency (p<0.1) to become stronger later during the day. The transition from D to L did not increase DA release significantly. When switching from F to D, DA release decreased by 17%. This effect was stronger in the late afternoon (p<0.01). The transition from L to D did not result in changes of DA release. Conclusions: This is the first time that in vivo microdialysis is applied to investigate retinal DA release during the light period in zebrafish kept under normal cyclic light. The results of our in vivo experiments are consistent with some findings by other studies using in vitro techniques. New is the finding that the effect of transitions DF and FD on DA release are stronger during the late afternoon.

Keywords: dopamine • retina: proximal (bipolar, amacrine, and ganglion cells)