PROLACTIN LEVELS IN RESTLESS LEGS SYNDROME

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Restless legs syndrome (RLS) is a disorder of unclear etiology. There is existing evidence primarily from clinical work that suggests there is an abnormality of dopamine function: Sinemet and the dopamine agonists are 95-99% effective in treating symptoms. PET and SPECT scanning results showed small but significant decreases in the D2 receptors and the DAT in the striatum. The purpose of this study is to look at an alternative dopamine sensitive system, prolactin secretion, as a possible biological marker for dopamine function and its characteristics in the RLS population. Prolactin secretion is under inhibitory dopamine control. Greenspan et al (1991) demonstrated a circadian pattern to the prolactin pulsatility in line with what is known about dopamine secretion. Dopamine is at its highest and prolactin at its lowest in the morning. Dopamine is at its lowest and prolactin is at its highest late night and early hours of the morning. In Restless legs syndrome the symptoms have a circadian pattern: worse at night minimal or absent in the morning. It has been postulated that circadian variations in the dopaminergic system within the brain are responsible for this circadian variation in symptoms. Decreasing dopamine at night leads to the onset of symptoms. Therefore, it would be appropriate to look at dopamine mechanisms which follow a circadian pattern, particularly those that follow the expected pattern of RLS symptoms. That is, with a decrease in dopamine at night, prolactin rises as do RLS symptoms. Both supposedly are due to a decrease in dopaminergic activity. One would therefore hypothesize that patients with restless legs syndrome would have increased mean prolactin levels, increased pulse height and increased pulse amplitude at night compared to age-matched controls. These are the measures, which were evaluated and found most sensitive to changes in dopaminergic activity in the Greenspan et al 1991 paper (1).