title: BOLD fMRI of C-Fiber Mediated Nociceptive Processing in Mouse Brain in Response to Thermal Stimulation of the Forepaws.
abstract: Functional magnetic resonance imaging (fMRI) in rodents enables non-invasive studies of brain function in response to peripheral input or at rest. In this study we describe a thermal stimulation paradigm using infrared laser diodes to apply noxious heat to the forepaw of mice in order to study nociceptive processing. Stimulation at 45 and 46°C led to robust BOLD signal changes in various brain structures including the somatosensory cortices and the thalamus. The BOLD signal amplitude scaled with the temperature applied but not with the area irradiated by the laser beam. To demonstrate the specificity of the paradigm for assessing nociceptive signaling we administered the quaternary lidocaine derivative QX-314 to the forepaws, which due to its positive charge cannot readily cross biological membranes. However, upon activation of TRPV1 channels following the administration of capsaicin the BOLD signal was largely abolished, indicative of a selective block of the C-fiber nociceptors due to QX-314 having entered the cells via the now open TRPV1 channels. This demonstrates that the cerebral BOLD response to thermal noxious paw stimulation is specifically mediated by C-fibers.
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; Center for Neurosciences, University and ETH Zürich, Zurich, Switzerland.
authors.forename: Simone C
authors.initials: SC
authors.lastname: Bosshard
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Stuker
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Constantin
authors.initials: C
authors.lastname: von Deuster
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Aileen
authors.initials: A
authors.lastname: Schroeter
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; Center for Neurosciences, University and ETH Zürich, Zurich, Switzerland; Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Rudin
mesh_terms: D000818:Animals; D005260:Female; D005552:Forelimb / Q000502:physiology*; D006358:Hot Temperature; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D059225:Nociception / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*