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Responses of human skin blood vessels to synthetic histamine analogues |
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| Authors: | I. Robertson and M. W. Greaves |
| Abstract: | 1 The vascular responses of human skin to two synthetic analogues of histamine, 2-methyl histamine (an H1-receptor agonist) and 4-methyl histamine (an H2-receptor agonist) have been studied in vivo. 2 Both compounds evoked dose-related erythema, 2-methyl histamine but not 4-methyl histamine causing erythema mediated by an axon reflex, thus suggesting that the axon reflex and direct vasodilator action of histamine are due to H1 and H2 actions respectively. 3 The H1-receptor antagonist chlorpheniramine inhibited erythema due to 2-methyl histamine. Cimetidine, an H2-receptor antagonist, had no effect on the reaction to 2-methyl histamine. In contrast, the erythema reaction to 4-methyl histamine was suppressed by both cimetidine and chlorpheniramine. 4 Although both histamine analogues caused wealing, this was not dose-related within the dose range used, and neither chlorpheniramine nor cimetidine caused detectable suppression of wealing responses to either histamine analogue. 5 These results lend further support to the view that human skin blood vessels possess H2 as well as H1 receptors. |
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