Fish can get Insomnia too

Yahoo News reports that Zebrafish lacking a hypocretin receptor sleep 30% less than fish without this mutation:
LOS ANGELES (Reuters) - Fish might not have eyelids, but they do sleep, and some suffer from insomnia, scientists reported on Monday.

California scientists studying sleep disorders in humans found that some zebrafish, a common aquarium pet, have a mutant gene that disrupts their sleep patterns in a way similar to insomnia in humans.

Zebrafish with the mutant gene slept 30 percent less than fish without the mutation. When they finally drifted off they remained asleep half as long as the normal fish, the researchers at the Stanford University School of Medicine said.

The mutant fish lacked a working receptor for hypocretin, a neuropeptide that is secreted in normal fish by neurons in the region of the brain that controls hunger, sex and other basic behaviors.

The researchers, led by Emmanuel Mignot, said they would look for fish that have a mutation that causes them to oversleep or never sleep in the hope of discovering if sleep-regulating molecules and brain networks developed through evolution.

The study was published in Tuesday's edition of the Public Library of Science-Biology.

Hypocretin is the neurochemical linked to the narcolepsy-cataplexy syndrome; human narcoleptics (with cataplexy) have a hypocretin deficiency. Disturbed, fragmented nocturnal sleep is a common, underrecognized symptom of narcolepsy.

Narcolepsy without cataplexy is a poorly understood condition and we sleep doctors have no idea what causes most cases of this condition.