The influence of Type A behavior pattern on the response to the panicogenic agent CCK-4

Objectives: Review of the literature equivocally suggests that subjects wit h Type A behavioral pattern (TABP) compared to subjects with Type B behavio ral pattern display an increased sympathetic activity, a condition associat ed with sudden cardiac death. The objective of this study was to determine whether healthy subjects classified as Type A or Type B differed in their r eactivity to the beta1 and beta2 receptor agonist isoproterenol and to the panicogenic agent cholecystokinin-tetrapeptide (CCK-4). By comparing reacti vity to CCK-4 after pretreatment with placebo or propranolol, a beta1 and b eta2 receptor antagonist, the role of the beta adrenergic system in the hyp othesized increased response of Type A subjects to CCK-4 was also assessed. Methods: The study used a randomized, double-blind, placebo-controlled des ign. Twenty-seven Type A or B subjects were included in the study. The reac tivity to isoproterenol was assessed with the CD25 of isoproterenol (i.e., the intravenous dose of isoproterenol necessary to increase the heart rate of 25 bpm). The panic symptom response and the cardiovascular response to b olus injection of 50 mug of CCK-4 was assessed in subjects pretreated with either propranolol or placebo infusions prior to the CCK-4 challenge. An ad ditional group of subjects was recruited and these subjects received a plac ebo infusion pretreatment before an injection of placebo. Results: The CD25 was significantly greater in Type A subjects than in Type B subjects. No d ifference was found among the groups on behavioral sensitivity to the CCK-4 challenge. However, CCK-4-induced maximum increase in heart rate was great er in Type A subjects. Conclusion: Our finding that Type A subjects exhibit ed greater CD25 of isoproterenol and greater increases in heart rate follow ing CCK-4 administration compared to Type B subjects suggests that peripher al beta -receptor sensitivity may be increased in individuals with TABP. (C ) 2001 Elsevier Science Inc. All rights reserved.