title: Nitric oxide-haemoglobin interaction: a new biochemical hypothesis for signal changes in fMRI.
abstract: A new hypothesis on the origin of activation-induced signal changes in functional magnetic resonance imaging (fMRI) is presented, involving transient formation of paramagnetic species, i.e. methaemoglobin (Hb+) and nitrosylhaemoglobin (Hb-NO), by reaction of nitric oxide (NO) with oxy-(Hb-O2) and deoxyhaemoglobin (Hb). Hb+ and Hb-NO, generated in erythrocytes, were found to produce marked concentration-dependent signal intensity changes when examined by T1-, T2- and T2*-weighted MRI. Intravenous administration of ascorbic acid (3 g) to healthy volunteers, to specifically reduce any Hb+ formed during brain activation, markedly decreased fMRI signal changes during standard tasks, suggesting a blood flow-independent effect produced by the reductant. These results open a new perspective on the fMRI evaluation of physiological processes associated with task-specific activation of brain structures.
authors.affiliation: Institute of Radiology, University of Naples Federico II, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Di Salle
authors.forename: P
authors.initials: P
authors.lastname: Barone
authors.forename: H
authors.initials: H
authors.lastname: Hacker
authors.forename: F
authors.initials: F
authors.lastname: Smaltino
authors.forename: M
authors.initials: M
authors.lastname: d'Ischia
mesh_terms: D001921:Brain / Q000502:physiology*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009569:Nitric Oxide / Q000737:chemistry*
chemical_list: D006454:Hemoglobins; D009569:Nitric Oxide