Medicinal plants of the genus Aconitum are one of the most commonly used herbs in traditional medicine in East Asia to treat conditions related to the heart, pain, or inflammation. However, these herbs are also dangerous as accidental poisoning due to misuse is a recurring issue. These plants contain a number of diester‐diterpenoid alkaloid compounds and aconitine is the most abundant and active one. This study investigated neurotoxicity of aconitine to zebrafish embryos in early development in relation to serotonin regulation. Experimental results showed that aconitine exposure (1, 10, and 100 μM) increased frequency of coiling behavior in zebrafish embryos in a dose‐dependent manner and this effect can be triggered by either exposure to 5‐hydroxytryptamine 1A (5‐HT1A) receptor agonist (±)‐8‐hydroxy‐2‐(dipropylamino)tetralin (8‐OH‐DPAT) or overexpression of serotonin receptor 5‐htr1ab. At the same time, coiling behavior caused by aconitine exposure could be rescued by co‐exposure to 5‐HT1A receptor antagonist WAY‐100635 Maleate (WAY100635) and knockdown of 5‐htr1ab using morpholino. Exposure to aconitine also significantly increased serotonin receptor 5‐htr1ab and 5‐htr1bd gene expression at 24 h post fertilization (hpf), but decreased their expression and protein expression of the serotonin receptor at 96 hpf with the high dose. These results suggest that neurotoxicity caused by aconitine is mediated through the 5‐HT receptor.

Borneol is an example of traditional Chinese medicine widely used in Asia. There are different isomers of chiral borneol in the market, but its toxicity and effects need further study. In this study, we used zebrafish embryos to examine the effects of exposure to three isomers of borneol [(À)-borneol, (+)-borneol, and isoborneol] on heart development and the association with Na + /K + -ATPase from 4 h postfertilization (4 hpf). The results showed that the three isomers of borneol increased mortality and decreased hatching rate when the zebrafish embryo developed to 72 hpf. All three isomers of borneol (0.01-1.0 mM) significantly reduced heart rate from 48 to 120 hpf and reduced the expression of genes related to Ca 2+ -ATPase (cacna1ab and cacna1da) and Na + /K + -ATPase (atp1b2b, atp1a3b, and atp1a2).At the same time, the three isomers of borneol significantly reduced the activities of Ca 2+ -ATPase and Na + /K + -ATPase at 0.1 to 1.0 mM. (+)-Borneol caused the most significant reduction (p < 0.05), followed by isoborneol and (À)-borneol. Na + /K + -ATPase was mainly expressed in otic vesicles and protonephridium. All three isomers of borneol reduced Na + /K + -ATPase mRNA expression, but isoborneol was the most significant (p < 0.01). Our results indicated that (+)-borneol was the least toxic of the three isomers while the isoborneol showed the most substantial toxic effect, closely related to effects on Na + /K + -ATPase.