Peripheral-type benzodiazepine receptor binding sites in platelets of patients with panic disorder associated to separation anxiety symptoms.

RATIONALE: Although it is still a matter of debate whether panic disorder (PD) and separation anxiety (SA) are associated or causally linked disorders, some investigators have suggested that SA may be a specific subtype of panic-agoraphobic spectrum. Several psychiatric disorders, including PD, are associated with lower levels of peripheral-type benzodiazepine receptor (PBR).
OBJECTIVES: The aim of the present study was to evaluate the kinetic binding parameters of the specific PBR ligand, PK 11195, in platelets from patients with PD in relation to the presence and severity of adulthood SA.
METHODS: Using the specific radioligand, [(3)H] PK 11195, the kinetic binding parameters of PBR were determined on platelet membranes of 27 adult outpatients with a DSM-IV diagnosis of PD and 18 healthy controls. Patients were assessed with the SCID-I, the Panic Disorder Severity Scale, the Structured Clinical Interview for Separation Anxiety Symptoms and the Adult Separation Anxiety Checklist.
RESULTS: PD patients had significantly lower PBR density than controls. However, the lower density was only evident in the subgroup of PD patients who also fulfilled the DSM-IV criteria for adult separation anxiety disorder. PBR density was negatively correlated with each of the two SA scales total scores.
CONCLUSIONS: Patients with SA symptoms had significantly lower densities of PBRs. PBR expression might become a useful biological marker of these two associated conditions.