Dopamine response to psychosocial stress in chronic cannabis users: A PET study with 11 C-(+)-PHNO

Abstract

A number of addictions have been linked with decreased striatal dopamine (DA) receptor availability and DA release. Stress has a key role in cannabis craving, as well as in modulation of dopaminergic signaling. The present study aimed to assess DA release in response to a laboratory stress task with 11 C-(+)-PHNO positron emission tomography in cannabis users (CU). Thirteen healthy CU and 12 healthy volunteers (HV) were scanned during a sensorimotor control task (SMCT) and under a stress condition using the validated Montreal imaging stress task (MIST). The simplified reference tissue model (SRTM) was used to obtain binding potential (BP ND) in striatal subdivisions: limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST). Stress-induced DA release (indexed as a percentage of reduction in 11 C-(+)-PHNO BP ND) between CU and HV was tested with analysis of variance. SMCT BP ND was significantly higher in CU compared with HV in the AST (F=10.38, p=0.003), LST (F=4.95, p=0.036), SMST (F=4.33, p=0.048), and whole striatum (F=9.02, p=0.006). Percentage of displacement (change in BP ND between SMCT and MIST PET scans) was not significantly different across groups in any brain region, except in the GP (-5.03±14.6 in CU, compared with 6.15±12.1 in HV; F=4.39, p=0.049). Duration of cannabis use was significantly associated with stress-induced 11 C-(+)-PHNO displacement by endogenous DA in the LST (r=0.566, p=0.044), with no effect in any other brain region. In conclusion, despite an increase in striatal BP ND observed during the control task, chronic cannabis use is not associated with alterations in stress-induced DA release. © 2013 American College of Neuropsychopharmacology. All rights reserved.