PERIPHERAL BENZODIAZEPINE RECEPTORS ARE DECREASED DURING COCAINE WITHDRAWAL IN HUMANS

In the present study, homovanillic acid in plasma (pHVA) and benzodiaz epine receptors (H-3-PK11195 binding) in neutrophil membranes were det ermined in blood obtained from cocaine-dependent (DSM-III-R) adult mal e inpatients at baseline (within 72 hr of last cocaine use) and after 3 weeks of cocaine abstinence, and normal controls. The mean (+/- SEM) pHVA at baseline (10.3 ng/ml +/- 1.1) was similar to normals and did not change after 3 weeks of cocaine abstinence. Similarly, the binding indices of benzodiazepine receptors in cocaine-dependent subjects as a group were not significantly different than in normal controls. In 1 0 cocaine-dependent subjects, however, where both blood samples were a vailable, the number of H-3-PK11195 binding sites was significantly (p < 0.05) decreased after 3 weeks of cocaine abstinence (mean +/- sem: B-max = 6371 +/- 657 fmol/mg protein) compared with baseline (B-max = 7553 +/- 925 fmol/mg protein), although there were no differences in t he binding affinity (mean +/- sem: K-D = 8.6 +/- 1.2 nmol/L after 3 we eks of abstinence compared with 8.1 +/- 1.0 nmol/L at baseline). These preliminary results suggest that peripheral benzodiazepine receptors may play an important role in the pathophysiology of cocaine withdrawa l in cocaine-dependent human subjects.