Histamine H3 receptors are expressed in the central nervous system and to a lesser extent the peripheral nervous system, where they act as autoreceptors in presynaptic histaminergic neurons and control histamine turnover by feedback inhibition of histamine synthesis and release.[5] The H3 receptor has also been shown to presynaptically inhibit the release of a number of other neurotransmitters (i.e. it acts as an inhibitory heteroreceptor) including, but probably not limited to dopamine, GABA, acetylcholine, noradrenaline, histamine and serotonin.
The gene sequence for H3 receptors expresses only about 22% and 20% homology with both H1 and H2 receptors respectively.
There is much interest in the histamine H3 receptor as a potential therapeutic target because of its involvement in the neuronal mechanism behind many cognitive disorders and especially its location in the central nervous system.[6][7]
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