title: Dopamine D3 receptor specifically modulates motor and sensory symptoms in iron-deficient mice.
abstract: Restless legs syndrome (RLS) is a common neurological disorder whose exact pathophysiological mechanism remains unclear despite the successful use of dopaminergic treatment and recent discovery of predisposing genetic factors. As iron deficiency has been associated with RLS for some patients and there is evidence for decreased spinal dopamine D(3)-receptor (D3R) signaling in RLS, we aimed at establishing whether D3R activity and iron deficiency share common pathways within the pathophysiology of RLS sensory and motor symptoms. Using a combined mouse model of iron deficiency and dopamine D(3)-receptor deficiency (D3R-/-), circadian motor symptoms were evaluated by continuous recording of spontaneous wheel running activity. Testing the acute and persistent pain responses with the hot-plate test and formalin test, respectively, assessed sensory symptoms. A 15 week iron-deficient (ID) diet alone increased acute and persistent pain responses as compared to control diet. As compared to C57BL/6 (WT), homozygous D3R-/- mice already exhibited elevated responses to acute and persistent pain stimuli, where the latter was further elevated by concurrent iron deficiency. ID changed the circadian activity pattern toward an increased running wheel usage before the resting period, which resembled the RLS symptom of restlessness before sleep. Interestingly, D3R-/- shifted this effect of iron deficiency to a time point 3-4 h earlier. The results confirm the ability of iron deficiency and D3R-/- to evoke sensory and motor symptoms in mice resembling those observed in RLS patients. Furthermore this study suggests an increase of ID-related sensory symptoms and modification of ID-related motor symptoms by D3R-/-.
authors.affiliation: Department of Clinical Neurophysiology, University Medical Centre Göttingen, 37075 Göttingen, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Dowling
authors.forename: Florian
authors.initials: F
authors.lastname: Klinker
authors.forename: Christine
authors.initials: C
authors.lastname: Stadelmann
authors.forename: Kenan
authors.initials: K
authors.lastname: Hasan
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
authors.forename: David
authors.initials: D
authors.lastname: Liebetanz
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D007839:Functional Laterality / Q000235:genetics; D007501:Iron / Q000097:blood; D000090463:Iron Deficiencies; D008124:Locomotion / Q000235:genetics / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009069:Movement Disorders / Q000209:etiology* / Q000235:genetics; D010146:Pain / Q000209:etiology* / Q000235:genetics; D010147:Pain Measurement / Q000379:methods; D010812:Physical Stimulation / Q000009:adverse effects; D020671:Posterior Horn Cells / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011930:Reaction Time / Q000235:genetics; D050637:Receptors, Dopamine D3 / Q000172:deficiency / Q000502:physiology*; D012148:Restless Legs Syndrome / Q000097:blood / Q000150:complications* / Q000235:genetics; D013116:Spinal Cord / Q000473:pathology
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D050637:Receptors, Dopamine D3; D007501:Iron