title: The dopaminergic system in patients with functional dyspepsia analysed by single photon emission computed tomography (SPECT) and an alpha-methyl-para-tyrosine (AMPT) challenge test.
abstract: OBJECTIVE
  Functional dyspepsia (FD) is a chronic condition characterized by upper abdominal symptoms without an identifiable cause. While the serotonergic system is thought to play a key role in the regulation of gut physiology, the role of the dopaminergic system, which is important in the regulation of visceral pain and stress, is under-studied. Therefore, this study investigated the dopaminergic system and its relationship with drinking capacity and symptoms in FD patients.
  
  
  METHODS
  In FD patients and healthy volunteers (HV) the dopaminergic system was investigated by in-vivo assessment of central dopamine D2 receptors (D2Rs) with [(123)I]IBZM SPECT and by an acute, but reversible, dopamine depletion alpha-methyl-para-tyrosine (AMPT) challenge test. A nutrient drink test was performed to investigate the association between maximal ingested volume, evoked symptoms, and D2Rs.
  
  
  RESULTS
  The HV subjects comprised 12 women and 8 men (mean age 31 ± 3 years), and the FD patients comprised 5 women and 3 men (mean age 39 ± 5 years). The FD patients had a lower left plus right average striatal binding potential (BP(NP)) for the caudate nucleus (p = 0.02), but not for putamen (p = 0.15), which in the FD patients was correlated with maximal ingested volume (r = 0.756, p = 0.03). The D2R BP(NP) in the putamen was correlated with nausea (r = 0.857, p = 0.01). The acute dopamine depletion test, however, failed to reveal differences in prolactin release between the FD patients and the HV subjects.
  
  
  CONCLUSIONS
  These preliminary data suggest that chronic rather than acute alterations in the dopaminergic system may be involved in the pathogenesis of FD. Further studies are required to reproduce our novel findings and to evaluate to what extent the dopaminergic changes may be secondary to abnormalities in serotonergic pathways.
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Breg
authors.initials: B
authors.lastname: Braak
authors.forename: Jan
authors.initials: J
authors.lastname: Booij
authors.forename: Tamira K
authors.initials: TK
authors.lastname: Klooker
authors.forename: Rene M J
authors.initials: RM
authors.lastname: van den Wijngaard
authors.forename: Guy E E
authors.initials: GE
authors.lastname: Boeckxstaens
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001549:Benzamides; D016022:Case-Control Studies; D004298:Dopamine / Q000172:deficiency / Q000378:metabolism*; D004326:Drinking; D004415:Dyspepsia / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period / Q000187:drug effects; D011388:Prolactin / Q000378:metabolism; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult; D019805:alpha-Methyltyrosine / Q000494:pharmacology*
chemical_list: D001549:Benzamides; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D019805:alpha-Methyltyrosine; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; D011388:Prolactin; D004298:Dopamine