Interesting. Here is the paper. (It's not copyrighted).
lol...They tested the effect of kava on worms (and also mutant worms...). The results are unexpected because according to the paper:
"The inhibitory-excitatory balance at the C elegans NMJ is maintained by the opposing actions of GABA and ACh. When the level of ACh signaling (excitation) is substantially greater than the level of GABA transmission (inhibition) at the C elegans NMJ, this results in muscle hypercontraction, which can manifest as a convulsion or paralysis. In our study, we showed that treatment of C elegans with kavalactones resulted in convulsions and paralysis (Figure 1). We hypothesized that these responses are indicative of elevated or prolonged ACh transmission at the NMJ."
Kava is normally thought of as acting in a GABAergic way, so this result is the opposite of what one would expect.
Interestingly, they noted that kavain has a different effect on worms than the other KLs.