Table 4.

D₁ receptor.

References	N (ketamine vs. controls)	Ketamine subjects (ketamine use- other substance use-comorbid disorders)	Controls	Significant differences ketamine subjects compared to controls	Statistic measure	Correlation
Narendran et al. (2005)	28 (14–14) PET-scan with radio-active ligand.	Mean ketamine use: 0.75 g/week 4.1 years Mean age 25 years Male/female 10/4 Route of administration was not mentioned 71% smokers. Absence of DSM-IV axis I diagnosis other than ketamine or cannabis abuse or dependence.	Drug-free controls Mean Age 25 years Male/female 9/5 43% smokers No history of neurologic or psychiatric illnesses incl. substance abuse.	Higher binding potential for D1 receptor in dorsolateral prefrontal cortex.	[11C]NNC 112 binding potential ml/g	Positive correlation between higher D1 binding potential and amount of consumed ketamine (p = 0.005).

PET, positron-emitted tomography; DSM-IV, Diagnostic and Statistical Manual of Mental Disorders, 4th Edition.