Two hypothalamic systems, the histaminergic and hypocretin neurons, are parts of the wake-promoting network. Hypocretin activates strongly the histaminergic neurons, whereas the effects of hypocretin neurons on histaminergic system are not well known. In narcoleptic humans, the hypocretin neurons degenerate, whereas the number of histamine-synthesizing neurons increases. The significance and mechanism of this increase are not known.
The seminar will describe regulation of the number of histamine neurons, and how dopamine regulates the number of both histamine and hypocretin neurons in zebrafish. Zebrafish has very similar histamine and hypocretin systems as mammals. The newly described cerebral dopamine neurotrophic factor regulates both the dopaminergic system and the wake-promoting systems. Potential mechanisms of these interactions are discussed.