H3 antagonist
Encyclopedia
An H3-receptor antagonist is a classification of drugs
used to block the action of histamine
at the H3 receptor. Unlike the H1 and H2 receptors which have primarily peripheral actions, but cause sedation
if they are blocked in the brain, H3 receptors are primarily found in the brain and are inhibitory autoreceptors located on histaminergic nerve terminals, which modulate the release of histamine
. Histamine release in the brain triggers secondary release of excitatory neurotransmitters such as glutamate and acetylcholine
via stimulation of H1 receptors in the cerebral cortex
. Consequently unlike the H1 antagonist antihistamines which are sedating, H3 antagonists have stimulant
and nootropic
effects, and are being researched as potential drugs for the treatment of neurodegenerative conditions such as Alzheimer's disease
.
Examples of selective H3 antagonists include clobenpropit
, ABT-239
, ciproxifan
, and A-349,821
.
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
used to block the action of histamine
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
at the H3 receptor. Unlike the H1 and H2 receptors which have primarily peripheral actions, but cause sedation
Sedation
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure...
if they are blocked in the brain, H3 receptors are primarily found in the brain and are inhibitory autoreceptors located on histaminergic nerve terminals, which modulate the release of histamine
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
. Histamine release in the brain triggers secondary release of excitatory neurotransmitters such as glutamate and acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
via stimulation of H1 receptors in the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
. Consequently unlike the H1 antagonist antihistamines which are sedating, H3 antagonists have stimulant
Stimulant
Stimulants are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...
and nootropic
Nootropic
Nootropics , also referred to as smart drugs, brain steroids, memory enhancers, cognitive enhancers, and intelligence enhancers, are drugs, supplements, nutraceuticals, and functional foods that improve mental functions such as cognition, memory, intelligence, motivation, attention, and concentration...
effects, and are being researched as potential drugs for the treatment of neurodegenerative conditions such as Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
.
Examples of selective H3 antagonists include clobenpropit
Clobenpropit
Clobenpropit is a histamine H3 receptor antagonist. It has neuroprotective effects via stimulation of GABA release in the brain....
, ABT-239
ABT-239
ABT-239 is an H3-receptor inverse agonist developed by Abbott. It has stimulant and nootropic effects, and has been investigated as a treatment for ADHD, Alzheimer's disease, and schizophrenia. ABT-239 is more active at the human H3 receptor than comparable agents such as thioperamide, ciproxifan,...
, ciproxifan
Ciproxifan
Ciproxifan is an extremely potent histamine H3 inverse agonist/antagonist.The histamine H3 receptor is an inhibitory autoreceptor located on histaminergic nerve terminals, and is believed to be involved in modulating the release of histamine in the brain...
, and A-349,821
A-349,821
A-349,821 is a potent and selective histamine H3 receptor antagonist . It has nootropic effects in animal studies, although there do not appear to be any plans for clinical development at present and it is currently only used in laboratory research....
.