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Histamine is a neurotransmitter that is released from histaminergic neurons which project out of the mammalian hypothalamus. The cell bodies of these neurons are located in a portion of the posterior hypothalamus known as the tuberomammillary nucleus (TMN).
The histamine receptors are a class of G protein–coupled receptors which bind histamine as their primary endogenous ligand. [1] [2] Histamine receptors are proteins that bind with histamine, a neurotransmitter involved in various physiological processes. There are four main types: H1, H2, H3, and H4.
The neurotransmitters implicated in the control of nausea and vomiting include acetylcholine, dopamine, histamine (H1 receptor), substance P (NK-1 receptor), and serotonin (5-HT3 receptor). There are also opioid receptors present, which may be involved in the mechanism by which opiates cause nausea and vomiting.
Mouse-models and other research demonstrated that reducing histamine concentration in the H3R causes tics, but adding histamine in the striatum decreases the symptoms. [ 22 ] [ 23 ] [ 24 ] The interaction between histamine (H3-receptor) and dopamine as well as other neurotransmitters is an important underlying mechanism behind the disorder.
Histamine H 1 receptors are activated by endogenous histamine, which is released by neurons that have their cell bodies in the tuberomammillary nucleus of the hypothalamus. The histaminergic neurons of the tuberomammillary nucleus become active during the 'wake' cycle, firing at approximately 2 Hz; during slow wave sleep , this firing rate ...
In the peripheral nervous system, one of the primary roles of norepinephrine is to stimulate the release of the stress hormone epinephrine (i.e. adrenaline) from the adrenal glands. [31] Norepinephrine is involved in the fight-or-flight response [32] and is also affected in anxiety disorders [33] and depression. [34]
Histamine is a ubiquitous messenger molecule released from mast cells, enterochromaffin-like cells, and neurons. [5] Its various actions are mediated by histamine receptors H 1, H 2, H 3 and H 4. The histamine receptor H 2 belongs to the rhodopsin-like family of G protein-coupled receptors.
In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission, gastric acid secretion and immune response. [1] [2] Histidine decarboxylase is the sole member of the histamine synthesis pathway, producing histamine in a one-step reaction. Histamine cannot be generated by any other known enzyme.