Evaluation of Evans Blue extravasation as a measure of peripheral inflammation

Plasma extravasation is one of the characteristic symptoms of an inflammatory response and of neurogenic inflammation, a phenomenon which occurs following nerve damage, and can lead to significant changes in the control of the cutaneous circulation (1). Evans Blue binds with high affinity to serum albumin, and the complex has been often used to quantitatively assess the extent of extravasation that accompanies peripheral and neurogenic inflammation (2,3). Here we present a protocol for evaluating Evans Blue extravasation in rodents with the aid of local application of capsaicin to initiate a neurogenic response exciting the local nociceptors, causing pain, axon reflex vasodilatation and plasma extravasation due to local release of inflammatory mediators. The method is inexpensive, precise and efficient, and can be adapted to assess extravasation in a range of experimental pathological conditions such as parotitis (4) or craniofacial muscle inflammation (5), and their dependence on different proteins, receptors or pharmacological treatments (6-9), in addition to those eliciting neurogenic inflammation.