A PET study of D2 dopamine receptor density at different phases of the menstrual cycle

Behavioral and biochemical studies in animals indicate that central dopaminergic neurotransmission may be modulated by sex steroids. This may be the mechanism underlying the suggested association between estrogen and schizophrenia. The aim was to examine if different levels of sex steroids during the menstrual cycle are associated with variations in D2 dopamine receptor density as measured with positron emission tomography (PET) and [11C]raclopride. Five healthy women were examined, one during two subsequent follicular phases and four during two different phases of their menstrual cycle. In none of the women did the difference in putamen to cerebellum (P/C) ratios (-11 to 10%) exceed the difference in P/C ratios previously reported in test-retest analyses in men (-11 to 9%). The findings do not support the conclusion that there is a menstrual-cycle-dependent variation in D2 receptor density detectable with single PET examinations and [11C]raclopride. Furthermore, a stable P/C ratio throughout the menstrual cycle indicated a stable D2 receptor occupancy in schizophrenic women treated with antipsychotic drugs. Repeated PET examinations of schizophrenic women known to deteriorate during particular phases of their menstrual cycle may further contribute to our understanding of the association between schizophrenia and sex steroids.