STRIATAL DOPAMINE, DOPAMINE TRANSPORTER, AND VESICULAR MONOAMINE TRANSPORTER IN CHRONIC COCAINE USERS

Depletion of striatal dopamine (DA) has been hypothesized to explain s ome of the neurological and psychiatric complications of chronic use o f cocaine, including increased risk for neuroleptic-precipitated movem ent disorders. We measured levels of DA, as well as two DA nerve termi nal indices, namely, the DA transporter (DAT) and the vesicular monoam ine transporter (VMAT2) in autopsied brain of 12 chronic cocaine users . Mean DA levels were normal in the putamen, the motor component of th e striatum; however, 4 of the 12 subjects had DA values below the lowe r limit of the control range. DA concentrations were significantly red uced in the caudate head (head, -33%; tail, -39%) with a trend for red uction in nucleus accumbens (-27%). Striatal DAT protein (-25 to -46%) and VMAT2 (-17 to -22%) were reduced, whereas DAT determined by [H-3] WIN 35,428 binding was normal. In conclusion, our data suggest that ch ronic cocaine use is associated with modestly reduced levels of striat al DA and the DA transporter in some subjects and that these changes m ight contribute to the neurological and psychiatric effects of the dru g.