Figure 4. Pharmacological inhibition of dopamine signaling blocks skin penetration in the human-parasitic hookworm A. ceylanicum.

A. Haloperidol inhibits skin penetration, and dopamine rescues this phenotype. Tracks show two representative worms from each treatment group; for the haloperidol-treated group, one representative worm that completed penetration and one randomly selected worm that did not complete penetration are shown. Representative worms were defined as in Fig. 3A. The key shows the behavioral motifs that were tracked. B. Haloperidol treatment of A. ceylanicum iL3s inhibits skin penetration and exogenous dopamine (DA) rescues this behavioral phenotype. Bar graph shows the percentage of iL3s that were treated with either the vehicle (control), 160 μM haloperidol, 10 mM DA, or 160 μM haloperidol + 10 mM DA that completed penetration. n = 14–30 iL3s per condition. ****p<0.0001, *p<0.05, ns = not significant, Fisher’s exact test with a Bonferroni correction for multiple comparisons. C. Haloperidol reduces the percentage of time that A. ceylanicum iL3s spend pushing and puncturing the skin, and this effect is rescued by addition of exogenous DA. Violin plot depicts the percentage of time that worms from each treatment group spent engaging in pushes or punctures. n = 9–29 iL3s per condition. ***p<0.001, **p<0.01, ns = not significant, Kruskal-Wallis test with Dunn’s post-test. iL3s that had initiated penetration by the time the recording started were excluded from this analysis. D. Haloperidol inhibits punctures and DA rescues this behavioral phenotype. Violin plot depicts the time taken by worms from each treatment group to puncture the skin since placement on skin. The dotted line at y = 5 indicates the time at which the assay ended; the dots above this line indicate worms that failed to puncture the skin by the end of the assay period. n = 18–30 iL3s per condition. **p<0.01, *p<0.05, ns = not significant, Kruskal-Wallis test with Dunn’s post-test. For C-D, dots depict individual worms, dashed lines indicate medians, and dotted lines indicate interquartile ranges. Behavioral parameters plotted in B-D were obtained from 4 independent replicate experiments.