Platelets of humans, as well as of other primates and some cats, aggregate in response to adrenaline. Scrutton et al. (1981) observed decreased responsiveness to adrenaline in platelets from 5 apparently normal, unrelated human subjects. In 4 of ... Platelets of humans, as well as of other primates and some cats, aggregate in response to adrenaline. Scrutton et al. (1981) observed decreased responsiveness to adrenaline in platelets from 5 apparently normal, unrelated human subjects. In 4 of these, the trait was shown to be inherited (with 1 instance of male-to-male transmission). In 3 of the probands and their affected relatives, depressed responsiveness to collagen and vasopressin, but normal responsiveness to ADP and thrombin, was observed. Mixing experiments excluded the existence of a circulating inhibitor of platelet function. None of the 'affected' persons had a bleeding disorder.