Transient knock-down of kcna2 reduces sleep in larval zebrafish

In the current study we set out to determine the effects of morpholino oligonucleotide (MO) knock-down of kcna2 on sleep-wake cycles in zebrafish. The results were compared to a non-overlapping MO injection, Dec2, who's mutant is also linked with a short sleep phenotype. Four groups of fish were used in the experiment: naïve fish, and fish injected with either control, kcna2, or Dec2 MO. All groups underwent 24-h behavioral monitoring of sleep-wake cycles at four and seven days-post-fertilization (dpf). First, we established an immobility dependent, sleep related, increase in arousal thresholds at both 4 and 7 dpf. Secondly, we show that kcna2 MO injected fish exhibit significantly less sleep behavior than controls and naïve fish, whereas Dec2 MO injections had similar but less severe effects. Finally, using kcna2 MO injected fish only, we turn to local field recordings at the level of the telencephalon and tectum opticum and rule out that the knock-down resulted in a non-specific increase in neural excitability that would mask sleep behavior.