Histamine containing neurons

Panula, P., Yang, H. Y. Costa, E. (1984). Histamine-containing neurons in the rat hypothalamus. Proc. Natl. Acad. Sci. USA 81, 2572-6. 

Histamine-containing neurons, located in the tuberomammillary nuclei (TMN) of the posterior hypothalamus, stimulate cortical activation through... 

Figure 6.2 The location and distribution of the histamine-containing neurons in the brain. These neurons are localized in the tuberomammiUaiy nucleus within the posterior hypothalamus and send projections throughout the brain. Abbreviations Hi, hippocampus Hy, hypothalamus IC, inferior colliculus OB, olfactory bulb SC, superior colliculus SI, substantia innominata St, striatum TH, thalamus TMN, tuberomammillary nucleus. Adapted from Watanabe Yanai (2001).

Some CNS stimulants have an effect on the same systems that are involved in wakefulness, including glutamate-, NE-, DA-, 5-HT-, histamine-, hypocretin- and ACh-containing neurons. This group includes molecules such as cocaine, amphetamine, and nicotine. The sleep-promoting systems are concentrated in the medial part of the brainstem, dorsal reticular substance of the medulla, anterior hypothalamus, and basal forebrain (Jones 2005). Other stimulants, such as caffeine and theophylline, block some sleep-inducing mechanisms. Modafinil is also a CNS stimulant with an unknown mechanism of action. 

Ascending histamine containing fibres originating from the reticular formation are considered important in arousal. Histaminergic neurons cease firing with the onset of sleep. Histamine antagonists (for the treatment of allergies) are... 

Figure 1. Histamine-containing tuberomammillary neurons and nerve fibers in normal human posterior hypothalamus.

Histamine is stored within and released from neurons but a neuronal transporter for histamine has not been found. Newly synthesized neuronal histamine is transported into TM neuronal vesicles by the vesicular monoamine transporter VMAT2 [16]. Both in vivo and in vitro studies show that depolarization of nerve terminals activates the exocytotic release of histamine by a voltage- and calcium-dependent mechanism. Once released, histamine activates both postsynaptic and presynaptic receptors. Unlike the nerve terminals from other amine transmitters, however, histaminergic nerve terminals do not exhibit a high-affinity uptake system for histamine [5, 9, 23]. Astrocytes may contain a histamine transport system. 

In the mucosa of the gastrointestinal tract histamine is present in enterochromaffin cells. These cells are thought to contain the histamine which is involved in the stimulation of gastric acid secretion. In the central nervous system there are histaminergic neurons. 

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