Changes in muscarinic acetylcholine receptor binding in skin slices of cholinergic urticaria

Muscarinic acetylcholine receptors were studied in slices of unaffected skin and in lymphocyte membranes from 3 patients with cholinergic urticaria and 5 healthy subjects using receptor autoradiography and the radioligand [3H]quinuclidinyl benzilate binding technique. Autoradiography revealed that muscarinic acetylcholine receptors were located in regions with sweat glands. The distribution of receptors did not differ qualitatively between patients and controls. However, the maximum number of muscarinic acetylcholine receptors was reduced in skin from patients with cholinergic urticaria, by 44% as compared with the controls, whereas the binding affinity was not affected. Muscarinic cholinergic binding in lymphocyte membrane fractions obtained from patients with cholinergic urticaria did not differ statistically from that of healthy control persons.