Articles: histamine.
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Histaminergic neurons of the hypothalamic tuberomammillary nuclei (TMN) send projections to the whole brain. Early anatomical studies described histaminergic neurons as a homogeneous cell group, but recent evidence indicates that histaminergic neurons are heterogeneous and organized into distinct circuits. We addressed this issue using the double-probe microdialysis in freely moving rats to investigate if two compounds acting directly onto histaminergic neurons to augment cell firing [thioperamide and bicuculline, histamine H(3)- and gamma-aminobutyric acid (GABA)(A)-receptor (R) antagonists, respectively] may discriminate groups of histaminergic neurons impinging on different brain regions. ⋯ The presence of H(3)-Rs on histaminergic neurons was assessed using double-immunofluorescence with anti-histidine decarboxylase antibodies to identify histaminergic cells and anti-H(3)-R antibodies. Confocal analysis revealed that all histaminergic somata were immunopositive for the H(3)-R. This is the first evidence that histaminergic neurons are organized into functionally distinct circuits that influence different brain regions, and display selective control mechanisms.
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Acta Odontol. Scand. · Jan 2009
Response of human oral mucosa and skin to histamine provocation: laser Doppler perfusion imaging discloses differences in the nociceptive nervous system.
To investigate the existence of histamine-excitable nerve fibers in the oral mucosa and to compare the response to histamine provocation in healthy volunteers with that in a small group of patients with chronic oral pain. ⋯ Intra-oral flare could be induced by activating histamine-excitable nerve fibers. Both duration and intensity of the flare were considerably less pronounced than in the control skin site. Histamine application was not clearly associated with itch.
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Randomized Controlled Trial Comparative Study
Subcutaneous histamine versus botulinum toxin type A in migraine prophylaxis: a randomized, double-blind study.
To compare the efficacy and tolerability of the subcutaneous administration of histamine and botulinum toxin type A (BoNTA) in migraine prophylaxis. ⋯ This randomized study demonstrated that both histamine and BoNTA are similarly effective and well tolerated in reducing or eliminating headache in migraine prophylaxis. Low doses of histamine applied subcutaneously may represent a novel and effective therapeutic alternative in migraine patients and lay the clinical and pharmacological groundwork for the use of H3 agonist in migraine prophylaxis.
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Acta Derm. Venereol. · Jan 2009
Impact of scratching on itch and sympathetic reflexes induced by cowhage (Mucuna pruriens) and histamine.
Cowhage and histamine, both applied via spicules, were used to induce itch. The quality and intensity of the sensations, axon reflex flare, sympathetic skin vasoconstrictions and the interference of scratching with itch processing were studied. Axon reflex flare reactions were measured by laser Doppler imaging and reflex vasoconstrictions in the finger were recorded by laser Doppler flowmetry. ⋯ Cowhage induced a sharper itch sensation and stronger vasoconstrictor reflexes. These findings support the notion that both agents activate different pathways. The differences in sympathetic reflex induction and in the modulation by scratching indicate differential central nervous processing.
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This is the first investigation of the central processing of itch in the brain in 8 subjects with atopic dermatitis (AD) in comparison to 6 healthy controls (HC), comparing histamine-induced itch related activations in the frontal, prefrontal, parietal, cingulate cortex, thalamus, basal ganglia and cerebellum. ⋯ We interpret our findings as possible central correlates of changes in the motor system in subjects with chronic itch, with activation of the basal ganglia possibly correlating to the vicious itch-scratch-circle in subjects with chronic itching skin diseases. However, further neuroimaging studies in healthy subjects and also in different skin diseases are needed to understand the complex mechanisms of the processing of itch.