27 August 2014
Vol 6, Issue 251

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ONLINE COVER Sore Paw Pads. To search for new drugs to alleviate pain, researchers often test candidate drugs on rat paws. An irritating substance—such as carrageenan extracted from seaweed or Irish moss—is injected into the paws, and the touch sensitivity of the inflamed paw (shown here) is tested with tiny hairs applied to its surface—an index of pain. Promising drugs (one is described by Zambelli et al. in this issue) can reduce pain in rats' irritated paws. [CREDIT: B. SMALL/STANFORD UNIVERSITY]