[Modulation of cortical pain processing by cyclooxygenase inhibition: a functional MRI study].
BACKGROUND
Little is known about changes in brain activity with pharmacological modulation of hyperalgesia. Therefore, we sought to investigate the cerebral processing of hyperalgesia and acute pain using functional magnetic resonance imaging (fMRI) and pharmacological modulation with cyclooxygenase (COX) inhibitors.


METHODS
As an experimental model, we used UVB-induced mechanical hyperalgesia. In a double-blind, placebo-controlled, randomized study, acetylsalicylic acid (ASA) and parecoxib were administered to 14 healthy volunteers. Corresponding brain activity changes were assessed using fMRI.


RESULTS
Psychophysically, parecoxib showed both analgesic and antihyperalgesia effects, whereas ASA had only antihyperalgesic effects in the experimental model. Analgesic effects were found in primary (S1) and secondary (S2) somatosensory cortices and anterior parts of the anterior cingulate cortex (ACC). In contrast, antihyperalgesic effects were mainly detected in S1, parietal association cortices, and the ACC.


CONCLUSIONS
This study provides new evidence for the involvement of COX inhibitors in modulating the cerebral activity associated with acute pain and hyperalgesia. Our results hint at a differential modulation of brain areas under either analgesia or antihyperalgesia.
Herrndobler
F
F
Anästhesiologische Klinik, Universitätsklinikum Erlangen, Erlangen, Deutschland.
Koppert
W
W
Ringler
R
R
Maihöfner
C
C
D000208:Acute Disease; D000328:Adult; D000700:Analgesics / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004292:Dominance, Cerebral / Q000187:drug effects / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D005625:Frontal Lobe / Q000187:drug effects / Q000503:physiopathology; D006179:Gyrus Cinguli / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D007555:Isoxazoles / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010296:Parietal Lobe / Q000187:drug effects / Q000503:physiopathology; D011601:Psychophysics; D013003:Somatosensory Cortex / Q000187:drug effects / Q000503:physiopathology
D000700:Analgesics; D016861:Cyclooxygenase Inhibitors; D007555:Isoxazoles; C409945:parecoxib; D001241:Aspirin