In patients with
panic disorder and /or
agoraphobia (PDA) an increased sensitivity of central 5-HT2C receptors and a decreased responsiveness of 5-HT1A receptors has been postulated. In the present study, neuroendocrine challenges were performed using oral doses of the non-selective
5-HT2C agonist m-chlorophenylpiperazine (
m-CPP) (0.4 mg/kg), the selective
5-HT1A antagonist ipsapirone (0.3 mg/kg), and placebo in 40 patients with PDA and 12 healthy controls in order to compare 5-HT2C and 5-HT1A-specific psychobehavioural and neuroendocrine response patterns. At baseline, all psychobehavioural variables and the plasma concentration of
noradrenaline (NE) were significantly increased in the patient group compared to the controls. The administration of
m-CPP or
ipsapirone was followed by comparable psychological symptoms and, in 55% of all patients,
panic attacks. In comparison to the control subjects, patients were characterized by significantly higher psychological reactions to both challenge agents and a significantly higher NE response to
m-CPP. In the patient group, there was also a trend towards an increased
cortisol response after administration of
m-CPP and a decreased
cortisol and
hypothermia response after administration of
ipsapirone compared to the control group. The neuroendocrine findings of our study support earlier reports of opposite changes in the responsiveness of 5-HT2C and 5-HT1A-related receptors in PDA patients. The behavioural
hypersensitivity to both,
m-CPP and ipsapiron, shows that the provocation of anxiety and other psychological symptoms might be influenced by