Dopamine transporter availability in medication free and in bupropion treated depression: a 99mTc-TRODAT-1 SPECT study

BACKGROUND

Bupropion is thought to exert its antidepressive effect by blocking the dopamine transporter (DAT). The purpose of this study was to evaluate the DAT activity in depressed patients by means of 99mTc-TRODAT-1 SPECT in relation to the efficacy of bupropion treatment.

METHODS

In 12 healthy controls and 16 depressed patients the baseline DAT activity was examined. Nine of the 16 patients went through an additional second SPECT investigation, after 4 weeks of bupropion treatment.

RESULTS

In the depressed patients, the baseline DAT striatum-occipital ratio (SOR) (1.04+/-.36, mean+/-SD) was not significantly different from that in the control group (1.12+/-.33) (p>.05). Correlation was found between baseline SOR and HAM-D score change (r=-.745, p=.02) of the bupropion treated patients. The average DAT occupancy due to the bupropion treatment was 20.84+/-27.7%. No significant correlation between the therapeutical effectiveness and the occupancy was observed.

LIMITATIONS

One of the limiting factors of our study has been the lack of drug monitoring.

CONCLUSIONS

In good agreement with other PET studies, we found 20.84% DAT occupancy during bupropion treatment. The lack of correlation between the efficacy of therapy and occupancy of DAT may raise the question as to whether other mechanisms are involved in the effect of bupropion.

[Change of dopamine transporter activity (DAT) during the action of bupropion (in depression)]

Bupropion has an antidepressant effect through blocking the dopamine transporter. By 99mTc-TRODAT-SPECT, we measured the baseline DAT activity of depressed patients. After 3 weeks' bupropion treatment we studied the change in DAT activity, which corresponds to the occupancy of bupropion. The average occupancy of bupropion on DAT was similar to the international findings at 20.84% in 9 depressed patients.

The prognostic value of dopamine receptor occupancy by [123I]IBZM-SPECT in schizophrenic patients treated with quetiapine

BACKGROUND

In the present study D2 receptor occupancy was investigated in quetiapine treated schizophrenic patients for the detection of a relationship between the scintigraphic pattern and clinical signs and symptoms.

MATERIAL AND METHODS

In 10 schizophrenic patients [123I]IBZM-SPECTs were performed during the introduction of quetiapine therapy (600-800 mg/day) and during a lower maintenance dose (200-400 mg/day). The patients' clinical follow-up was continued for 1 year. For the evaluation of SPECT images, visual interpretation was performed and striatum/occipital lobe (S/O) activity ratio was calculated.

RESULTS

The initial striatum/occipital ratio was significantly higher in patients with relapse compared to the others (1.86 +/- 0.17, 1.53 +/- 0.15, p < 0.01). The decreasing striatum/occipital ratio (increasing D2 receptor occupancy) on the 2nd SPECT was a predictive factor for the relapse.

CONCLUSIONS

D2 receptor occupancy and its changes during quetiapine therapy were related to the prognosis of the treatment efficacy.

[Imaging of dopamine transporter with Tc99m-Trodat-SPECT in movement disorders]

99mTc-TRODAT-1 is a new, technetium based radiopharmaceutical that selectively binds to the dopamine transporters. The aim of the study was to evaluate the dopamine transporter status in movement disorders.

METHODS

In eight healthy volunteers (age range 22-58 years), 28 patients with Parkinson's disease (age range 42-80 years), 10 patients with Parkinsonian syndrome (age range 51-79 years) and 13 patients with essential tremor (age range 43-71 years) were 99mTc-TRODAT-SPECT tests performed. The results were evaluated visually and semiquantitatively.

RESULTS

The visual assessments were concordant with those of the semiquantitative in each case. The 99mTc-TRODAT uptake of the striatum was referenced to the cerebellum, the frontal and occipital cortex. The best deviation was found in aspect of the occipital cortex. The striatum/occipital ratio was the following: healthy volunteers: 2.12 +/- 0.27; Parkinson's disease: 1.52 +/- 0.27; Parkinsonian syndrome: 1.57 +/- 0.26; essential tremor: 2.06 +/- 0.69. The striatal dopamine transporter availability was significantly lower in subjects with Parkinson's disease or Parkinsonian syndrome compared to the control subjects. There was no difference between healthy volunteers and patients with essential tremor. Using discriminant analysis, the discriminant function had significantly different values in the group of Parkinson's disease than in Parkinsonian syndrome: f = -3.675 x caud/occipit + 6.293 x put/occipit -2.548.

CONCLUSION

99mTc-TRODAT-SPECT is able to visualise the presynaptic dopaminergic degeneration. This method itself can be useful in differential diagnosis in some type of movement disorders.