Smoking a single cigarette does not produce a measurable reduction in brain MAO B in non-smokers.
Positron emission tomography (PET) studies with [11C]L-deprenyl-D2 have shown that brain monoamine oxidase (MAO) B is 40% lower in smokers than in non-smokers. Here we investigated whether MAO B inhibition can be detected after smoking a single cigarette. Eight normal healthy non-smokers (35 +/- 11 years) received two PET studies 2 h apart with [11C]L-deprenyl-D2, one at baseline and the second 5-10 min after the subject had smoked a single cigarette. Plasma nicotine and expired carbon monoxide (CO) were measured prior to smoking and 10 min after smoking completion as an index of tobacco smoke exposure. A three-compartment model was used to calculate lambda k3, a model term which is proportional to MAO B activity and which is derived from the time course of carbon-11 in the brain and the time course of the radiotracer in the plasma and K1, the plasma-to-brain transfer constant (for [11C]L-deprenyl-D2) which is related to brain blood flow. Subjects experienced difficulty inhaling and became dizzy and/or nauseous after smoking. Plasma nicotine averaged 11.6 +/- 5.5 ng/ml and expired CO averaged 8 +/- 10 ppm after smoking. The average lambda k3 and K1 for 11 different brain regions did not differ significantly between baseline and smoking. These results indicate that the reduction in MAO B in smokers probably occurs gradually and requires chronic tobacco smoke exposure.
Fowler
J S
JS
Brookhaven National Laboratory, Upton, NY 11973, USA. fowler@bnl.gov
Wang
G J
GJ
Volkow
N D
ND
Franceschi
D
D
Logan
J
J
Pappas
N
N
Shea
C
C
MacGregor
R R
RR
Garza
V
V
D000328:Adult; D001921:Brain / Q000201:enzymology*; D002250:Carbon Radioisotopes; D005260:Female; D005731:Ganglionic Stimulants / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008995:Monoamine Oxidase / Q000032:analysis*; D008996:Monoamine Oxidase Inhibitors / Q000627:therapeutic use; D009538:Nicotine / Q000097:blood / Q000494:pharmacology*; D012642:Selegiline / Q000627:therapeutic use; D012907:Smoking; D014055:Tomography, Emission-Computed
D002250:Carbon Radioisotopes; D005731:Ganglionic Stimulants; D008996:Monoamine Oxidase Inhibitors; D012642:Selegiline; D009538:Nicotine; D008995:Monoamine Oxidase