Evidence that L-deprenyl treatment for one week does not inhibit MAO A or the dopamine transporter in the human brain

In this study, we investigated whether treatment with L-deprenyl, a selecti ve monoamine oxidase B (MAO B) inhibitor, also inhibits MAO A or the dopami ne transporter in the human brain. Six normal volunteers (age 46 +/- 6 yrs) had two PET sessions, one at baseline and one following L-deprenyl (10 mg/ day) for 1 week. Each session included one scan with [C-11]clorgyline (to a ssess MAO A) and one scan 2 hours later with [C-11]cocaine (to assess dopam ine transporter availability). A 3-compartment model was used to compare th e plasma-to-brain transfer constant, K, (a:function of blood flow) and Xk, (a kinetic term proportional to brain MAO A) before and after treatment. Do pamine transporter availability was measured as the ratio of distribution v olumes of the striatum to cerebellum (DVR) which is equal to Bmax/K-D + 1. L-Deprenyl treatment for 1 week did not affect either brain MAO A activity or dopamine transporter availability. There was a non-significant trend for an increase in K, after L-deprenyl. These results confirm that L-deprenyl after one week of treatment at doses typically used clinically is selective for MAO B and that it does not produce a measurable affect on the dopamine transporter, suggesting that MAO A inhibition and dopamine transporter blo ckade do not contribute tb its pharmacological effects. (C) 2001 Elsevier S cience Inc. All rights reserved.