Fig. 4. Effect of SCH-23390 and SKF-81297 on 6 dpf zebrafish larvae’s electric response. (A) Exposure timeline of zebrafish larvae. Electric-induced (B) RD and (C) TBF of zebrafish larvae exposed to no chemical (control), 50 μM SKF-81297, 0.6 μM SCH-23390, and SKF-81297 after exposure to 0.6 μM SCH-23390. Lines within the box mark the median data points. Upper and lower box boundaries are the 75th and the 25th percentiles, respectively. Whiskers are the highest and lowest data points obtained. *: P<0.05, **: P<0.01, ***: P<0.001. n=15 larvae per experimental condition in three independent trials, for a total of N = 45 larvae tested per group.
We then determined the effects of two D2-like selective compounds on zebrafish electric response (Fig. 4). When larval electric-induced locomotor response was recorded after exposure to quinpirole (a D2-like selective agonist), increased activity was observed (P-value<0.05). Treatment with quinpirole raised RD and TBF by 49% and 24%, respectively. DMSO vehicle did not alter zebrafish larvae locomotor activity from the control level, ensuring that DMSO can be used as solvent for haloperidol in our assay. Haloperidol exposure decreased the RD and TBF by 49% and 33%, respectively and completely abolished the locomotor activities at 50 μM (Data not shown). Posttreatment with quinpirole caused a 55% increase in electric-induced RD and a 70% rise in TBF. No statistical difference was observed between the control group and the post-treated larvae (P-value>0.05), verifying an improvement of locomotor activity under treatment of haloperidol-exposed zebrafish larvae with quinpirole due to an increase in DA concentration.