sensory and motor neuroscienceWatch this thread
How does H3 and H4 receptors treat brain disorders?
I do understand their roles in the brain however I don't get how they treat different brain diseases as all the articles state that this matter is yet to be studied and experimented via clinical trials.
I would appreciate the help
You are probs aware that H3 receptors are presynaptic receptors, i.e. they inhibit the histaminergic neurone itself, hence its agonists have a kind of antagonist effect to that of stimulation of an H1 or H2 receptor, in much the same manner as adrenergic alpha-2 receptors.
Also both H3 and H4 receptor action produce their effects by an action on GPCRs, in this case Gi OR G0 proteins, so that they reduce the action of adenylyl cyclase [producing less cAMP].
The last I knew, there were only a handful of agonists/antagonists at these receptors that were known, but none were approved for clinical use [please google the drugs in bold below to find out the latest situation].
H3 antagonists might now be approved for use in sleeping disorders, ADHD and Alzheimer's disease [examples known are thioperamide, and clobenpropit]. H3 receptors exist in the hypothalamus, basal ganglia and nucleus accumbens, and have have broad projections. Stimulation of H3 receptors in the CNS also reduce food intake, so they have a potential in the treatment of obesity.
H4 antagonists mostly have an indirect anti-inflammatory effect, so can probably be used peripheral. The only possible CNS use I can think of might be to treat neuropathic pain. EXAMPLES: thioperamide [in addition to its affinity for H3 receptors, also binds H4 receptors. Impentamine is an H4 receptor antagonist.
Hope this is slightly helpful!