Do organic solvents induce changes in the dopaminergic system? Positron emission tomography studies of occupationally exposed subjects.

OBJECTIVES

The objective of this study was to test the hypothesis that long-term occupational exposure to organic solvents may effect the levels and turnover of dopamine in man.

METHODS

A study was performed on 17 patients with neuropsychiatric symptoms due to occupational solvent exposure, and 11 healthy non-exposed male volunteers (controls). Positron emission tomography (PET) was used to assess striatal dopaminergic function, using L-[11C]DOPA, [11C]nomifensine and [11C]raclopride as tracers.

RESULTS

The rate of dopamine synthesis was significantly increased among subjects with occupational exposure to organic solvents compared with non-exposed controls. After controlling for the difference in age between exposed and controls, the effect of solvent exposure became less apparent and was reduced from +32% (P = 0.009) to +25% (P = 0.07). There were no differences with regard to the binding of [11C]nomifensine. Patients with and without the diagnosis of toxic encephalopathy did not differ with regard to their putaminal uptake of L-[11C]DOPA, [11C]nomifensine and [11C]raclopride.

CONCLUSION

The data support the hypothesis that long-term exposure to organic solvents may increase the rate of dopamine synthesis in the brain without affecting the number of presynaptic terminals or postsynaptic dopamine receptors.