The mechanism of the histamine-induced desensitization of guinea-pig ileum.

Histamine and the selective H1 receptor agonist 2-pyridylethylamine show cross-desensitization when tested in guinea-pig ileum. The H1 receptor blocking agent produces a smaller parallel shift in desensitized tissues when compared with non-desensitized controls. We conclude that desensitization in this system occurs at the receptor level and is reflected by a decreased sensitivity to both agonists and antagonists.