A new technique for screening drugs’ effects on zebrafish behavior is leading Harvard University scientists toward unexpected compounds and pathways that may control sleep and wakefulness in humans.
Appearing in the journal Science, the new research identifies several compounds with surprising effects on sleep and wakefulness in zebrafish. The research also suggests that despite the evolutionary gap between them, zebrafish and mammals may be remarkably similar in the neurochemistry underlying their rest/wake cycles.
"Many current drug discovery efforts rely on screening conducted outside the body," said Alexander F. Schier, PhD, professor of molecular and cellular biology at Harvard. "Although such screens can be successful, they cannot recreate the complex neuroscience of entire organisms. These limitations are particularly acute for behavior-altering drugs because brain activity cannot be modeled in a Petri dish or test tube."
Schier and other collaborators used their automated screening technique to monitor zebrafish sleep and wakefulness for 2 days after administering nearly 5,600 compounds, which created more than 60,000 distinct behavioral profiles. By applying clustering algorithms to organize these molecules, the researchers identified 463 drug candidates that significantly altered rest and wakefulness, many of which had not previously been known to have such effects.
"For instance, we found that a diverse set of anti-inflammatory compounds increased wakefulness during the day, with much less effect at night," said Schier. "Although these compounds have long been known to promote sleep during infection, this is an indication that the molecules that regulate the immune system may also play a role in setting normal daytime activity levels."
The anti-inflammatory agents found to affect sleep/wake cycles included cytokines, nonsteroidal anti-inflammatory drugs, and the immunosuppressant cyclosporine. Schier and colleagues also found calcium channel inhibitors that increased rest with minimal effects on waking behavior. A class of potassium channel blockers found in a wide variety of drugs, including antimalarials, antipsychotics, and antihistamines, were found to selectively increase wakefulness at night without affecting total rest.
"Behavioral profiling reveals nuanced relationships between drugs and their targets," Schier said. "It can characterize large classes of compounds and reveal differences in effectiveness, potential side effects, and combinatorial properties that might not otherwise be detected."