The placebo effect can be a blessing for patients and an annoying confound for experimenters. This week, two groups tried to localize the site(s) of action of placebo analgesia. Matre et al. show that spinal processing of pain is altered by placebo. A placebo effect emerged not only in patient reports of initial pain intensity, but also in the subsequent hyperalgesia. The latter is a consequence of central sensitization of spinal nociceptive neurons. In other work, Kong et al. used functional magnetic resonance imaging to visualize brain areas activated by the placebo effect generated by sham acupuncture needles. Interestingly, different regions were activated than previously seen with a placebo cream treatment of the skin, suggesting that placebo effects can arise from different brain pathways.
2. Amyloid Angiopathy in an
Elissa M. Robbins, Rebecca A. Betensky, Sarah B. Domnitz, Susan M. Purcell, Monica Garcia-Alloza, Charles Greenberg, G. William Rebeck, Bradley T. Hyman, Steven M. Greenberg, Matthew P. Frosch, and Brian J. Bacskai
â-amyloid (Aâ) deposits accumulate not only within the brain parenchyma, but also in cerebral arteries The vascular deposits of cerebral amyloid angiopathy (CAA) are often associated with lobar intracerebral hemorrhages in elderly patients, and are recapitulated in mouse models of Alzheimer disease (AD). This week Robbins et al. made use of methoxy- X04, the fluorescent dye that binds amyloid, to visualize the progression of CAA in real time. The arterial amyloid formed first as band-like deposits, then advanced mainly through propagation of existing deposits rather than formation of new deposits. This approach may be of use in examining treatments that affect the deposition and clearance of Aâ.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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