Age and gender effects of 11C-ITMM binding to metabotropic glutamate receptor type 1 in healthy human participants.

We examined possible age- and gender-related changes in binding of the selective antagonist N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-4-11C-methoxy-N-methylbenzamide (11C-ITMM) to metabotropic glutamate receptor type 1 in healthy human brains. Dynamic 11C-ITMM positron emission tomography scans (90 min) with serial arterial blood sampling were performed in 15 young and 24 older healthy adult volunteers. The total distribution volume (VT) of several brain regions was estimated with 2-tissue compartment model analysis. The VTs of the cerebellar cortex, parietal cortex, putamen, amygdala, and hippocampus in older adult participants were significantly higher than in young participants. The age-related VT increase was only observed in male participants. Our data suggest that an age-dependent increase in metabotropic glutamate receptor type 1 availability in several brain regions may exist predominantly in males.