[Effect of aging on in vivo binding of 11C-N-methylspiperone in living human frontal cortex].
Reduced in vivo binding of 11C-N-methylspiperone (NMSP) with age in the living human frontal cortex was demonstrated, with positron emission tomography (PET). Eleven normal male volunteers (22 to 72 years old) were assessed. The uptake of 11C-NMSP in the frontal cortex peaked 7-15 min after intravenous injection, and then gradually decreased until the end of this study. On the other hand in the cerebellum, the uptake of 11C-NMSP peaked 10 min and rapidly declined. We analyzed the data using a three compartment model and determined rate constants k3 and k4. And the binding potential of receptors was estimated as the ratio of k3 (association rate constant) to k4 (dissociation rate constant) value. The k3 and k4 values were calculated from nonlinear regression, given by the set of parameter values that minimized the deviation between the measured kinetics and model prediction. As an input function, we used the radioactivity in the cerebellum. A significant reduction in BP with age was observed. Though both k3 and k4 values were decreased with age, this decrease of BP was found to be mainly due to the reduced k3 values. These results indicated that numbers of binding sites (Bmax) of serotonin S2 receptors in frontal cortex might be decreased with age.
Yonezawa
H
H
Division of Clinical Research, National Institute of Radiological Sciences, Japan.
Iyo
M
M
Itoh
T
T
Fukuda
H
H
Yamasaki
T
T
Inoue
O
O
Suhara
T
T
Shinotoh
H
H
Nishio
M
M
Tohgi
H
H
D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D002250:Carbon Radioisotopes; D015259:Dopamine Agents / Q000493:pharmacokinetics*; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013134:Spiperone / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D014055:Tomography, Emission-Computed
D002250:Carbon Radioisotopes; D015259:Dopamine Agents; D013134:Spiperone; C039167:3-N-methylspiperone