Immediate effects of tDCS on the μ-opioid system of a chronic pain patient
- 1Headache and Orofacial Pain Effort, Biologic and Materials Sciences Department and MCOHR, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
- 2Faculdade de Medicina, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- 3Translational Neuroimaging Laboratory, Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
- 4Laboratory of Neuromodulation, Spaulding Rehabilitation Hospital, Harvard University, Boston, MA, USA
We developed a unique protocol where transcranial direct current stimulation (tDCS) of the motor cortex is performed during positron emission tomography (PET) scan using a μ-opioid receptor (μOR) selective radiotracer, [11C]carfentanil. This is one of the most important central neuromechanisms associated with pain perception and regulation. We measured μOR non-displaceable binding potential (μOR BPND) in a trigeminal neuropathic pain patient (TNP) without creating artifacts, or posing risks to the patient (e.g., monitoring of resistance). The active session directly improved in 36.2% the threshold for experimental cold pain in the trigeminal allodynic area, mandibular branch, but not the TNP patient’s clinical pain. Interestingly, the single active tDCS application considerably decreased μORBPND levels in (sub)cortical pain-matrix structures compared to sham tDCS, especially in the posterior thalamus. Suggesting that the μ-opioidergic effects of a single tDCS session are subclinical at immediate level, and repetitive sessions are necessary to revert ingrained neuroplastic changes related to the chronic pain. To our knowledge, we provide data for the first time in vivo that there is possibly an instant increase of endogenous μ-opioid release during acute motor cortex neuromodulation with tDCS.
Keywords: tDCS, PET, opioid receptors, neuroplasticity, trigeminal neuropathic pain, post-herpetic neuralgia
Citation: DosSantos MF, Love TM, Martikainen IK, Nascimento TD, Fregni F, Cummiford C, Deboer MD, Zubieta J-K and DaSilva AFM (2012) Immediate effects of tDCS on the μ-opioid system of a chronic pain patient. Front. Psychiatry 3:93. doi: 10.3389/fpsyt.2012.00093
Received: 20 June 2012; Accepted: 02 October 2012;
Published online: 02 November 2012.
Copyright: © 2012 DosSantos, Love, Martikainen, Nascimento, Fregni, Cummiford, Deboer, Zubieta and DaSilva. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Alexandre F. M. DaSilva, Headache and Orofacial Pain Effort, The Molecular and Behavioral Neuroscience Institute, University of Michigan, 205 Zina Pitcher Pl, Room 1021, Ann Arbor, MI 48109-5720, USA; Biologic and Materials Sciences, School of Dentistry, 1011 North, University Avenue, Room 1014A, Ann Arbor, MI 48109-1078, USA. e-mail: firstname.lastname@example.org