Age-related loss of extrastriatal dopamine D2-like receptors in women

Authors


Address correspondence and reprint requests to Valtteri Kaasinen, University of Turku, Department of Neurology, POB 52, FIN-20521, Turku, Finland. E-mail: valtteri.kaasinen@pet.tyks.fi

Abstract

Positron emission tomography (PET) studies have indicated that the in vivo availability of dopamine D2-like receptors declines with age in the human brain. Most of the studies have been carried out with healthy male subjects, or with subject groups containing both sexes. The authors have recently demonstrated that the availability of D2-like receptors in the frontal cortex is higher in women than in men. The present study was aimed to further examine this phenomenon. Thirty-seven healthy women (age range 22–78 years) were examined with PET and [11C]FLB 457, a high-affinity tracer for the extrastriatal D2-like receptors. A negative relationship between age and dopamine D2-like receptor availability was seen in the frontal cortex (decrease of 12% per decade of life), the temporal cortex (9%) and the thalamus (6%). A non-linear s-shape association explained the relationship only in the frontal cortex, while in other regions the association was linear. Neither oestradiol nor progesterone levels had a significant relationship with the [11C]FLB 457 uptake in any of the brain regions studied after the effect of age was partialled out. The results indicate that: (i) the extrastriatal D2-like receptor availability decreases with age in healthy women with the fastest rate in the frontal cortex and with the overall rate close to the rate reported in healthy men; (ii) around midlife (age 40–60 years) in women, the frontal receptor decline plateaus while the decline continues to be linear in other extrastriatal brain regions; and (iii) serum oestradiol or progesterone levels are not associated with cortical or thalamic D2-like receptor availability in women. The results may prove to be important in studies where the biochemical basis of clinical sex differences is examined in patients with dopamine-related neuropsychiatric disorders.

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