Effect of H1-and H2-receptor antagonists on cutaneous inflammation evoked by histamine analogues and UV radiation.

The effect of mepyramine, cimetidine and a combination of both types of histamine receptor antagonist on the cutaneous vasodilatation, increased vascular permeability and oedema formation associated with UV injury was quantitatively evaluated. The specificity of the histamine antagonists employed in this study was verified by examining their effect on the vascular changes produced by selective H1- and H2-receptor agonists. The immediate, transient increase in vascular permeability and hyperaemia evoked by UV radiation was substantially reduced by a combination of mepyramine and cimetidine whereas the vascular changes which comprise the delayed, prolonged phase of the inflammatory response remained unaltered by histamine receptor blockade. It is concluded that histamine plays a major role in mediating the initial, transient phase of UV-induced inflammation but does not appear to be involved in mediating the subsequent sustained vascular changes.