Measurement of regional brain metabolism

FDG is readily taken tip by this transport system, although the extent of uptake can be influenced by the concentration of plasma glucose, which competes with FDG for uptake. The efficiency of transport across the blood brain barrier is such that blood flow is generally not limiting for tracer delivery but the potential for a drug to have a direct vascular effect that influences tracer delivery should be considered. 

In a prototype experiment evaluating a psychoactive compound, brain metabolism would be measured during a control condition and following acute or chronic administration of a drug. To the extent that a drug interacts with sites that influence the excitability or inhibitory status of neurons, this can be detected as changes in regional brain metabolism. Examples of the results of such an experiment are depicted in Plate 6.1. 

Many compounds have been evaluated for their effects on brain metabolism (London, 1993). A surprisingly limited number of common regional metabolic effects have been seen within drug classes. Antipsychot ics, especially the older typical antipsychotics, tend to be associated with changes in striatal metabolism consistent with the high density of D2 dopamine receptors in those brain structures (Cohen et al.. 1999). On the other hand, quite different patterns of metabolic effects have been seen following acute doses with paroxetine and fluoxetine, both of which are selective serotonin 

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