“…5 Photomicrograph showing c-fos expression in animals irradiated at 3 W, in repeated exposure there is intense neuronal activation (a) marked with an asterisk and shown at high magnification (b); note slight c-fos activation in repeated exposure, nonirradiated animals (c, d).Calibration bar 100 lm (a ,c) and 50 lm (b, d) [20], has also been used experimentally to diminish pain [76,77] and to activate the hypothalamus-hypophysis in the treatment of various pathologies [78,79]. Recent studies have shown that the PVN plays an important role in analgesia [58,[80][81][82].…”