Articles: histamine.
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Comparative Study
The itch-producing agents histamine and cowhage activate separate populations of primate spinothalamic tract neurons.
Itch is an everyday sensation, but when associated with disease or infection it can be chronic and debilitating. Several forms of itch can be blocked using antihistamines, but others cannot and these constitute an important clinical problem. Little information is available on the mechanisms underlying itch that is produced by nonhistaminergic mechanisms. ⋯ Histamine or cowhage responsive STT neurons were found in both the marginal zone and the deep dorsal horn and were classified as high threshold and wide dynamic range. Unexpectedly, histamine and cowhage never activated the same cell. Our results demonstrate that the spinothalamic tract contains mutually exclusive populations of neurons responsive to histamine or the nonhistaminergic itch-producing agent cowhage.
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A considerable amount of evidence suggests that temporomandibular joint (TMJ) pain associated with temporomandibular disorder results, at least in part, from an inflammatory episode. Although histamine can cause pain, it is not clear whether this mediator induces nociception in the TMJ. In this study, we investigated the contribution of endogenous histamine to formalin-induced nociception in the TMJ of rats. ⋯ Finally, the administration of a sub-threshold dose of 5-HT (100 microg), but not of histamine (100 microg), elicited nociception in the TMJ previously challenged with the inflammatory agent carrageenan (100 microg). In conclusion, these data suggest that histamine induces TMJ nociception by an indirect mechanism involving endogenous release of 5-HT and activation of 5-HT(3) receptors on sensory afferents. It is proposed that histamine activates the H1 receptor to induce the release of 5-HT which depolarizes the nociceptor by activating 5-HT(3) receptor.
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Clinical therapeutics · May 2007
Randomized Controlled Trial Comparative StudyComparison of inhibition of cutaneous histamine reaction of ebastine fast-dissolving tablet (20 mg) versus desloratadine capsule (5 mg): a randomized, double-blind, double-dummy, placebo-controlled, three-period crossover study in healthy, nonatopic adults.
Ebastine is a long-acting, second-generation, selective histamine H1-receptor antagonist. A fast-dissolving tablet formulation of ebastine has been developed at 10- and 20-mg doses, with the intention of facilitating administration to patients experiencing problems with swallowing, including those confined to bed and elderly people, as well as those who may need to use ebastine when they do not have easy access to water to aid swallowing a tablet. ⋯ In this small study in healthy, nonatopic white subjects, inhibition of the response to histamine injection was significantly greater with the ebastine 20-mg fast-dissolving tablet compared with desloratadine 5-mg capsule and placebo after 1 and 5 days of administration. Most participants expressed an overall preference for the fast-dissolving tablet formulation over capsules. All study drugs were well tolerated.
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Biochemical pharmacology · Apr 2007
The brain H3-receptor as a novel therapeutic target for vigilance and sleep-wake disorders.
Brain histaminergic neurons play a prominent role in arousal and maintenance of wakefulness (W). H(3)-receptors control the activity of histaminergic neurons through presynaptic autoinhibition. The role of H(3)-receptor antagonists/inverse agonists (H(3)R-antagonists) in the potential therapy of vigilance deficiency and sleep-wake disorders were studied by assessing their effects on the mouse cortical EEG and sleep-wake cycle in comparison to modafinil and classical psychostimulants. ⋯ These data validate the hypothesis that H(3)R-antagonists, through disinhibition of H(3)-autoreceptors, enhancing synaptic histamine that in turn activates postsynaptic H(1)-receptors promoting W. Interestingly amphetamine and modafinil, despite their potent arousal effects, appear unlikely to depend on histaminergic mechanism as their effects still occurred in HDC KO-mice. The present study thus distinguishes two classes of wake-improving agents: the first acting through non-histaminergic mechanisms and the second acting via histamine and supports brain H(3)-receptors as potentially novel therapeutic targets for vigilance and sleep-wake disorders.
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Brain histamine is involved in a wide range of physiological functions such as regulation of sleep-wake cycle, arousal, appetite control, cognition, learning and memory mainly through the 4 receptor subtypes: H1, H2, H3 and H4. Neurons producing histamine, histaminergic neurons, are exclusively located in the tuberomammillary nucleus of the posterior hypothalamus and are transmitting histamine to almost all regions of the brain. Roles of brain histamine have been studied using animals including knock-out mice and human subjects. ⋯ Nowadays, H3 receptors have been thought to be a new target of drug treatment of various neuropsychiatric disorders. There are still many research topics to be investigated regarding molecular imaging of histamine and histamine receptors. The authors hope that this line of research contributes more for the promotion of QOL in patients and people in daily lives.