Articles: histamine.
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Invest. Ophthalmol. Vis. Sci. · Mar 2006
Randomized Controlled TrialIntravenous administration of diphenhydramine reduces histamine-induced vasodilator effects in the retina and choroid.
Intravenous administration of histamine causes an increase in choroidal blood flow (ChBF) and retinal vessel diameters in healthy subjects. The receptor mediating this response has not yet been identified. The present study was undertaken to clarify whether H1 receptor blockade with diphenhydramine affects the hemodynamic response of histamine in the choroid and the retina. ⋯ The present data confirm that histamine increases ChBF and retinal vessel diameters in healthy subjects. Administration of the H1 receptor blocker diphenhydramine significantly reduced histamine-induced changes in ocular perfusion parameters. These results strongly indicate that in the retina and choroid, H1 receptors are involved in the histamine-mediated hemodynamic effects in vivo.
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J. Invest. Dermatol. · Dec 2005
Noxious heat and scratching decrease histamine-induced itch and skin blood flow.
The aim of this study was to assess the effect of thermal stimuli or distal scratching on skin blood flow and histamine-induced itch in healthy volunteers. Twenty-one healthy volunteers participated in the study. Baseline measurements of skin blood flow were obtained on the flexor aspect of the forearm. ⋯ Cold pain and cooling reduced itch intensity, but neither affected histamine-induced skin blood flow. Sub-noxious warming the skin did not affect the skin blood flow or itch intensity. These findings suggest that heat pain and scratching may inhibit itch through a neurogenic mechanism that also affects skin blood flow.
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Endogenous histamine-releasing factors (HRFs) are involved in 30-60% of patients with chronic urticaria (CU). Evidence for their existence comes from in vivo studies of autoreactivity with the autologous serum skin test (ASST), in vitro immunoassays demonstrating autoantibodies against the immunoglobulin E (IgE) or the high affinity IgE receptor (FcepsilonRI) and serum-induced histamine release (HR) from basophils and mast cells. We have examined the correlation between the ASST and a new basophil histamine-releasing assay (the HR-Urtikaria test) in a group of well-characterized CU patients and subsequently determined the frequency of HR-Urticaria-positive sera from a larger population of CU patients. ⋯ Our studies have shown that the HR-Urticaria test has a good sensitivity and specificity for endogenous HRFs demonstrated by the ASST in patients with CU and that about one-third of unselected patients with CU have a positive result.
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Pediatric dermatology · Mar 2005
Randomized Controlled Trial Comparative StudyChildren's rating of itch: an experimental study.
Little is known about children's ability to assess itch. The present paper aimed to investigate the discriminative capacity of two itch rating scales in children. Sixty healthy children, 4 to 12 years of age, participated. ⋯ However, children 4 to 5 years of age rated the itch intensity (both scales) less well than those aged 6 to 12 years. The younger age group discriminated between saline and histamine, but not between the different histamine concentrations. In conclusion, children aged 6 to 12 years were able to discriminate between different itch stimulus strengths in a dose-dependent way with a 100-mm visual analog scale and a four-stepped verbal rating scale, indicating the validity of these scales for measurement of experimental itch in children 6 years or older.
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Experimental dermatology · Mar 2005
Inhibition of scratching behaviour caused by contact dermatitis in histidine decarboxylase gene knockout mice.
A neuronal system dedicated to itch consists of primary afferent and spinothalamic projection neurons. Histamine is thought to be one of the main mediators for the transmission of itch sensation. However, there are little available information on the role of histamine in scratching behaviour and sensory transmission of atopic dermatitis and chronic eczema. ⋯ The expression of c-Fos was specifically upregulated in HDC (+/+) mice in lamina I of the spinal dorsal horn following repeated DCP application. Scratching behaviour in chronic contact dermatitis in mice was thought mainly mediated with histamine. The afferent pathway of sensation in chronic contact dermatitis model may connect with the central nervous system through lamina I of the spinal dorsal horn.