H1-Histaminergic activation stimulates inositol-1-phosphate accumulation in chromaffin cells

Adrenal medullary chromaffin cells maintained invitro were prelabeled with [3H]inositol and the accumulation of [3H]inositol-1-phosphate, was determined following stimulation with a variety of pharmacological agents. Carbachol, bradykinin, and histamine produced significantly greater accumulation of [3H] inositol-1-phosphate over basal levels, with histamine producing the greatest effect. H1-histamine receptor antagonists, mepyramine, pyrilamine, tripelennamine and clemastine were all able to reduce or completely block the histamine response. The two specific H2-histamine receptor antagonists, cimetidine and ranitidine, had no effect on this response. Histamine dose-response characteristics in the presence of mepyramine and clemastine suggest the H1 antagonism to be competitive in nature.