Antiallergic Activity of Nylidrin Hydrochloride (RHC 3432-A)

Nylidrin hydrochloride has weak β-adrenergic agonist properties with rat mast cells, and shows synergy with 3-isobutyl-1-methylxanthine (IBMX) in raising intraceliular cAMP in purified mast cells; both of these properties can be blocked by dl-propranolol. However, the action of nylidrin hydrochloride as an inhibitor of histamine secretion from purified rat mast cells is not antagonized by dl-propranolol, nor is it potentiated by IBMX. Nylidrin-induced elevation of cellular cAMP in purified rat mast cells shows no correlation with nylidrin-induced inhibition of histamine release. Thus, nylidrin hydrochloride inhibits release of histamine from mast cells by a novel, non-adrenergic mechanism, which is not dependent on increased levels of cAMP.