| Autor: |
Frost, J. J., Douglass, K. H., Mayberg, H. S., Dannals, R. F., Links, J. M., Wilson, A. A., Ravert, H. T., Crozier, William C., Wagner, H. N. |
| Zdroj: |
Journal of Cerebral Blood Flow and Metabolism; June 1989, Vol. 9 Issue: 3 p398-409, 12p |
| Abstrakt: |
[11C]-Carfentanil is a high affinity opiate agonist that can be used to localize mu opiate receptors in humans by positron emission tomography (PET). A four-compartment model was used to obtain quantitative estimates of rate constants for receptor association and dissociation. PET studies were performed in five normal subjects in the absence and presence of 1 mg/kg naloxone. Arterial plasma concentration of [11C]-carfentanil and its labeled metabolites were determined during each PET study. The value of k3/k4= Bmax/kdwas determined for each subject in the presence and absence of naloxone. There was a significant reduction in the value of k3/k4from 3.4 ± 0.92 to 0.26 ± 0.13 in the thalamus (p< 0.01) and from 1.8 ± 0.33 to 0.16 ± 0.065 in the frontal cortex (p< 0.001). Mean values of frontal cortex/occipital cortex and thalamus/occipital cortex ratios were determined for the interval 35–70 min after injection when receptor binding is high relative to nonspecific binding. The relationship between the measured region/occipital cortex values and the corresponding values of k3/k4in the presence and absence of naloxone was: regions/occipital cortex = 0.95 + 0.74 (k3/k4) with r= 0.98 (n= 20). Simulation studies also demonstrated a linear relationship between the thalamus/occipital cortex or frontal cortex/occipital cortex ratio and k3/k4for less than twofold increases or decreases in k3/k4. Simulation studies in which thalamic blood flow was varied demonstrated no significant effect on the region/occipital cortex ratio at 35–70 min for a twofold increase or fourfold decrease in blood flow. Therefore, the region/occipital cortex ratio can be used to quantitate changes in k3/k4when tracer kinetic modeling is not feasible. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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