introduction: in the present study we attempted to investigate the alterations of cytological parameters of nrm (longaxis and intranuclear rods) in the absence of its excitatory vl pag afferent with or without the formalin pain model. materials and methods: we used male rats in 4 groups: 1- control group (n=4), 2- formalin group (n=4), 3- chemical lesion of vl pag by ibotenic acid (0.2 َl, 0.5 َl...