The effects of metoclopramide and cloxacepride on human mast cells from adenoidal tissues

Cloxacepride is an amide of the dopamine antagonist metoclopramide and has been reported to possess oral antiallergic properties in the rat PCA model. Both substances have now been tested in isolated mast cell preparations from human adenoidal tissues to determine whether any therapeutic antiallergic potential in man could be expected. Metoclopramide at concentrations 10(-5)-10(-3) M had no inhibitory effect but instead enhanced Con A-induced histamine release at concentrations greater than 10(-4) M. Cloxacepride at concentrations 10(-5)-10(-4) M significantly inhibited Con A-induced histamine release. This inhibitory effect was not diminished by increasing the preincubation time for up to 30 min. In contrast, cloxacepride concentrations greater than 4 x 10(-5) M caused a substantial histamine release. This effect could not be alleviated by an increase in the number of mast cells per sample. These results then suggest a very narrow range of therapeutic potential for cloxacepride.