Species differences in [C-11]clorgyline binding in brain

[C-11]Clorgyline selectively binds to MAO A in the human brain. This contra sts with a recent report that [C-11]clorgyline (in contrast to other labele d MAO A inhibitors) is not retained in the rhesus monkey brain [4]. To expl ore this difference, we compared [C-11]clorgyline in the baboon brain befor e and after clorgyline pretreatment and we also synthesized deuterium subst ituted [C-11]clorgyline (and its nor-precursor) for comparison, [C-11]Clorg yline was not retained in the baboon brain nor was it influenced by clorgyl ine pretreatment or by deuterium substitution, contrasting to results in hu mans. This suggests a species difference in the susceptibility of MAO A to inhibition by clorgyline and represents an unusual example of where the beh avior of a radiotracer in the baboon brain does not predict its behavior in the human brain. (C) 2001 Elsevier Science Inc. All rights reserved.