title: Sex differences in striatal presynaptic dopamine synthesis capacity in healthy subjects.
abstract: BACKGROUND
  There are sex differences in the clinical features of several neuropsychiatric illnesses associated with dopamine dysfunction. The effects of sex on brain dopaminergic function have been sparsely studied in human subjects using modern imaging techniques. We have previously reported that the apparent affinity of [(11)C]raclopride for striatal D(2) dopamine receptors in vivo is lower in women than in men, whereas D(2) receptor density is not different. This finding indirectly suggests that women have a higher synaptic concentration of dopamine in the striatum. We explored further the basis of this phenomenon in an independent study and hypothesized that striatal presynaptic dopamine synthesis capacity would also be elevated in women.
  
  
  METHODS
  A total of 23 healthy men and 12 healthy women (age range 20-60 years) were studied using positron emission tomography and [(18)F]fluorodopa.
  
  
  RESULTS
  Women had significantly higher striatal [(18)F]fluorodopa uptake (Ki values) than men. The difference was more marked in the caudate (+26%) than in the putamen (+12%). In addition, there was a negative correlation between striatal [(18)F]fluorodopa Ki values and age in men but not in women.
  
  
  CONCLUSIONS
  The results further substantiate sex differences in striatal dopaminergic function in humans. This finding may be associated with sex differences in vulnerability and clinical course of neuropsychiatric disorders with dopaminergic dysregulation, e.g., schizophrenia, alcohol dependence, and Parkinson's disease.
authors.affiliation: Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Laakso
authors.forename: Harry
authors.initials: H
authors.lastname: Vilkman
authors.forename: J
authors.initials: J
authors.lastname: Bergman
authors.forename: Merja
authors.initials: M
authors.lastname: Haaparanta
authors.forename: Olof
authors.initials: O
authors.lastname: Solin
authors.forename: Erkka
authors.initials: E
authors.lastname: Syvälahti
authors.forename: Raimo K R
authors.initials: RK
authors.lastname: Salokangas
authors.forename: Jarmo
authors.initials: J
authors.lastname: Hietala
mesh_terms: D000328:Adult; D000367:Age Factors; D003342:Corpus Striatum / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D004298:Dopamine / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017729:Presynaptic Terminals / Q000378:metabolism*; D012737:Sex Factors; D014055:Tomography, Emission-Computed
chemical_list: C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine; D004298:Dopamine