ABSTRACT
Data from animal studies suggest a functional relationship between the cholecystokinin-ergic (CCK) and the serotonergic (5-HT) system. There is increasing evidence that the cholecystokinin-4 (CCK4) challenge test could be a valid experimental model for panic attacks in man. The aim of the present study is twofold; 1) to validate this model further and 2) to shed more light on the putative CCK/5-HT interaction. To this end, we studied the effect of the selective serotonin reuptake inhibitor (SSRI) fluvoxamine on CCK4-induced panic attacks. Twenty-six panic disorder (PD) patients received, before and after a double blind 8-week treatment period with fluvoxamine (n = 17) or placebo (n = 9), a single blind bolus injection with 50 micrograms CCK4. Treatment with fluvoxamine (150 mg daily) significantly decreased the sensitivity of PD patients for CCK4 while placebo was without effect. Of the patients who responded to treatment, 83% no longer experienced a panic attack when rechallenged with CCK4, whereas in the non-responders group this was only 28%. In the fluvoxamine group the treatment response evaluated by the Hamilton Anxiety Scale (HAS) showed a statistically significant treatment effect. The results of this study strengthen the validity of the CCK4 test as an experimental human model for panic attacks and yield evidence supporting the hypothesis that both CCK and serotonin are implicated in the regulation of anxiety.