Viability varies based on duration and concentration of 6-OHDA exposure. Assessment of viability for four different protocols. The numbers below each group refer to the exposure age. Each individual data point refers to a new group of fish (Strain AB, n ? 24 per point). 6-OHDA, 6-hydroxydopamine.

6-OHDA selectively reduces th1 expression and induces a state of mitochondrial dysfunction through ROS introduction. RT-qPCR of four groups exposed to 30 ?M 6-OHDA for 24 h starting at day 3 (Strain AB, 24 embryos pooled per point). A significant reduction compared to controls occurred for th1, a marker for dopaminergic cells, and pink1, a marker for mitochondrial dysfunction (A). A significant increase compared to controls for sod1 and sod2, part of the cells ROS response, were observed (B). Three genes did not show a significant reduction: gad1b, a marker for GABAergic neurons; slc6a3, the DA transporter; and slc18a2, a vesicular monoamine transporter (C) (normalized to hprt1 and control, *Indicates a p < 0.05). ROS, reactive oxygen species; RT-qPCR, reverse transcriptase-quantitative polymerase chain reaction; DA, dopamine.

Fish exposed to 6-OHDA starting at 4 dpf do not show a reduction in th1. Vaz and coworkers had utilized a protocol with 24 h of treatment starting at 4 dpf. To assess if we could see expression changes using a similar timepoint, a RT-qPCR screen was performed in a single biological group. At doses that met viability and morphological criteria, 6-OHDA exposure did not induce a change greater than 0.2-fold (Strain AB, normalized to hprt1 and control, 24 fish pooled per sample). dpf, days postfertilization.

Extending exposure time of 10 ?M 6-OHDA to 48 h cannot produce a PD-like state. To determine if a longer exposure with a lower dose might alter expression, we assessed a 48-h treatment at 10 ?M 6-OHDA. Each point represents pooled RNA harvested from at least 15 fish from 3 different cohorts. (Strain AB, normalized to hprt1 and control). No significant expression differences were identified compared to control. PD, Parkinson's disease.

6-OHDA exposure decreases larval movement. A detailed analysis was performed of the movement of 6 dpf larval zebrafish following a 24-h treatment starting at 3 dpf with 30 ?M 6-OHDA. Blinded analysis of whether an animal moved over 10 min was first performed (A) with a significant reduction in number of animals that moved in exposed versus control (*Indicates a p < 0.05). Subsequent analysis of larvae that did move using Fiji (ImageJ) demonstrated no significant difference for distance moved (B), latency to first movement (C), time moved (D), and velocity (E).