Unable to complete accrual; elected to close the study in April 2008.

The purpose of this study is to determine in a preliminary manner whether successful therapy of hot flashes can be associated with changes in the serotonin transporter in the brain. The serotonin transporter is important in delivering serotonin into certain portions of the brains (serotonin is a chemical that is important in the control of body temperature, mood, sleep, and other functions).

Hot flashes represent the most common complaint among peri- and postmenopausal women. Over 60% of postmenopausal women experience hot flashes, and 10-20% of all postmenopausal women find them nearly intolerable. Despite the prevalence of hot flashes, their pathophysiology is not well understood. Treatment options include non-pharmacological approaches, hormonal interventions, and non-hormonal pharmacological agents. The most effective treatment for hot flashes is estrogen. The most promising non-hormonal treatments for hot flashes are selective serotonin or noradrenergic reuptake inhibitors (SSRI/SNRI). Although estrogen withdrawal is implicated in the initiation of hot flashes, and serotonin's role is well established in thermoregulation, the relationship between estrogen and serotonin is not known. Preclinical studies suggest that both estrogen and SSRI down regulate the serotonin transporter. Clinical studies that further delineate the relationship between effective treatments for hot flashes and the serotonin transporter may shed a new light into the pathophysiology of these symptoms and more importantly, into design of new-targeted treatments.

Inclusion Criteria:

• Postmenopausal women
• 7 or more hot flashes per day for at least 3 months
• Must be able to undergo magnetic resonance (MR) and PET imaging
• Must be able to receive either paroxetine or estrogen

Exclusion Criteria:

• No treatment with hormone therapy or other medications that affect estrogen within the past 3 months
• No evidence of a currently active cancer