FIGURES AND TABLES

Figure 1.

Typical spectrophotometric assay results exemplified by acetylcholine (ACh). Graph represents the absorbance at 420 nm over time for the cleavage of ACh (50 mg/mL) by acetylcholinesterase (AChE; 2 U/mL) in the presence of m-nitrophenol at 25 0.1°C. Data are collected at 6-second intervals and 10 minutes is allowed for temperature equilibration before the start of slope calculation. Slope of the absorbance change is calculated from 10 minutes to time X, where the absorbance change (A = A₁₀ - A_x) is >0.05 absorbance units. The linearity of A between 10 and X minutes was determined by linear least-squares regression (r ² > 0.98). The specific cleavage rate is calculated as the following: slope (A/min) divided by the enzyme concentration ([AchE] in U/mL) then multiplied by 1000 mL/L. For this example, A = 0.05 is achieved at 28.8 minutes so slope and linearity are calculated over the range of 10 to 30 minutes. Rate = -0.00263/2 (U/mL) 1000 (mL/L) = -1.31 A/min/U/L.

Figure 2.

Metabolism of radiotracers in mouse whole blood. Data are expressed as the percentage of authentic radiotracer remaining (means SD) at each time point. Curves for [¹¹C]2MBMP and [¹¹C]nVMP represent 1 chromatographic assay using blood from 3 animals. Curves for [¹¹C]nBMP and [¹¹C]PMP represent mean SD for 3 separate assays (n = 3 animals per assay).

Figure 3.

Time-activity curves for [¹¹C]nVMP and [¹¹C]nBMP in mouse brain. Female CD-1 mice were injected with 150 to 250 Ci of radiotracer then killed at various times postinjection. Data are expressed as the percent injected radioactivity dose per gram of tissue in striatum (STR) and cortex (CTX) at each time point. Each point is the mean SD for n 4 animals.

Figure 4.

Positron emission tomography (PET) imaging data for [¹¹C]PMP, [¹¹C]nBMP, and [¹¹C]nVMP in primates. Data represent time-activity curves and apparent enzymatic rate constants (k₃) (Koeppe et al., 1999) for regions of interest drawn over (A) striatum (caudate and putamen) and (B) cerebral cortex. Data are from a single PET scan for each radiotracer using the same animal for all three scans and have been normalized to the injected dose of radioactivity. [¹¹C]PMP data are from Kilbourn et al. (1996).

Table 1 - Chemical structures, acronyms, and analytical data for the 4-piperidinyl esters.

Table 2 - AChE-mediated cleavage rates for ChE substrates.

Table 3 - BuChE-mediated cleavage rates for all ChE substrates.