Plastic changes in sensory neurons that transmit nociception at central and peripheral level are responsible for the observed changes in the painful sensations during the inflammatory process. In fact, during inflammation or after the resolution occurs an increased excitability (sensitization) of a specific class of primary nociceptive neurons, due to the direct and indirect action of various inflammatory mediators. The small diameter nociceptive fibers (C fibers) have an important role in detecting noxious stimuli and initiating the transmission of painful information. C fibers are extremely important in the transmission of nociceptive information and appear to be fundamental in the genesis of inflammatory pain and are classified by morphological criteria in peptidergic and non-peptidergic. Peptidergic C fibers are able to produce and release neuropeptides such as substance P (SP) and calcitonin gene related peptide (CGRP) and express the receptor neurokinin 1 (NK-1R). The non peptidergic population of C-fibers expresses the P2X3 purinergic receptor and exhibit isolectin B4 binding. Another type of afferent fiber, A-delta fibers lead nociceptive information to specific areas in I and II lamina of the surface of spinal cord dorsal horn neurons and also for the V lamina, which code information innocuous stimuli so as harmful. A-delta fibers synthesize and release mediators such as glutamate and express neurofilament 200. Additionally, are not clear which types of afferent fibers participate in the induction of acupuncture analgesia effect. The point of controversy is if the type of afferent C fibers are involved. Thus, this design intended to elucidate the role of afferent fibers in the acupuncture-induced antinociception in different models of inflammatory hyperalgesia.Through this type of strategy will be carried out using molecular biology techniques to assess the effect of manual acupuncture or electroacupuncture of 2Hz or 100Hz on the expression of different markers in nociceptors, thus intend to contribute to the understanding of the functional role of afferents in the antinociception induced by acupuncture in the model of acute, persistent and neuropatic hyperalgesia.
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